Liquid crystal display device

ABSTRACT

A liquid crystal display device of an in-plane switching mode comprises at least optically anisotropic members (A) and (B) and liquid crystal cell disposed between a pair of polarizers having absorption axes disposed approximately perpendicularly to each other, wherein n zA &gt;n yA  and n xB &gt;n zB  (n xA , n xB :refractive indices (n) in the direction of the in-plane slow axis; n yA , n yB :n in the in-plane direction perpendicular to the above direction; n zA , n zB :n in the direction of thickness, each at 550 nm); the in-plane slow axes of (A) and (B) are approximately parallel or perpendicular to each other; and the in-plane slow axis of (A) is approximately parallel or perpendicular to the absorption axis of a polarizer closer to (A). The antireflection property, scratch resistance and durability are excellent, the angle of field is wide, and uniform display of images with great contrast can be achieved at any angle of observation.

TECHNICAL FIELD

The present invention relates to a liquid crystal display device. Moreparticularly, the present invention relates to a liquid crystal displaydevice which exhibits excellent antireflection property, scratchresistance and durability, provides a wide angle of field and achievesuniform display of images with great contrast at any angle ofobservation.

BACKGROUND ART

Liquid crystal display devices are characterized by the high quality ofimages, the small thickness, the light weight and the small consumptionof electric power and widely used for televisions, personal computersand automobile navigators. It has been pointed out that liquid crystaldisplay devices have a drawback in that brightness, color and contrastvary to a great extent and difficulty arises in watching images when theimages are observed at oblique angles.

To overcome the drawback, improvements in the design of the liquidcrystal cell itself have been studied, and a liquid crystal displaydevice of the in-plane switching mode is proposed as one of theimprovements (for example, Patent Reference 1). In accordance with theproposed technology, the angle of field is improved in comparison withthat of liquid crystal display devices of other modes. However, inaccordance with this technology, the arrangement of polarizer platesshifts from the cross-nichol arrangement depending on the angle ofobservation, and this causes a decrease in the angle of field due toleak of light although the decrease in the angle of field due to theliquid crystal molecules in the liquid crystal cell is relativelysuppressed. Moreover, further improvement is desired with respect to thenarrow angle of field due to the liquid crystal molecules in the liquidcrystal cell. Therefore, it is attempted that the decrease in thecontrast of images is suppressed by adding a means for opticalcompensation to the liquid crystal display devices of the in-planeswitching mode.

For example, a liquid crystal display device in which a sheet foroptical compensation is disposed between a liquid crystal cell and atleast one of polarizer plates, the sheet for optical compensation isoptically negatively uniaxial, and the optical axis is parallel to theface of the sheet, is proposed (Patent Reference 2).

As another liquid crystal display device of the in-plane switching mode,a liquid crystal display device in which a first polarizer plate, a filmfor optical compensation, a first substrate, a liquid crystal layer, asecond substrate and a second polarizer plate are disposed in thisorder, one of the polarizer plates has a transmission axis parallel tothe slow axis of the liquid crystal during the dark display of theliquid crystal layer, and the angle between the slow axis of the film inthe sheet for optical compensation and the transmission axis in one ofthe polarizer plates is 0 to 2° or 88 to 90°, is proposed (PatentReference 3).

However, none of these means are sufficient for providing a liquidcrystal display device which exhibits uniform display of images with agreat contrast at any angle of observation, and further improvement hasbeen desired.

[Patent Reference 1] Japanese Patent Application Laid-Open No. Heisei7(1995)-261152

[Patent Reference 2] Japanese Patent Application Laid-Open No. Heisei10(1998)-054982

[Patent Reference 3] Japanese Patent Application Laid-Open No. Heisei11(1999)-305217

DISCLOSURE OF THE INVENTION

The present invention has an object of providing a liquid crystaldisplay device which exhibits excellent antireflection property, scratchresistance and durability, provides a wide angle of field and achievesuniform display of images with great contrast at any angle ofobservation.

As the result of intensive studies by the present inventors to overcomethe above problems, it was found that the decrease in the contrast couldbe prevented and a liquid crystal display device of the in-planeswitching mode exhibiting a wide angle of field with a great contrastcould be obtained when two layers of optically anisotropic membershaving a specific refractive index were disposed at specific relativepositions with respect to a liquid crystal cell and a polarizer, andthat the decrease in the contrast could be prevented and a liquidcrystal display device of the in-plane switching mode exhibiting a wideangle of field with a great contrast could be obtained when opticallyanisotropic member (A) satisfying n_(z)>n_(y) and optically anisotropicmember (B) satisfying n_(x)>n_(z) were arranged at specific relativepositions with respect to the liquid crystal cell and a polarizer,wherein n_(x) represented the refractive index in the direction of thein-plane slow axis, n_(y) represented the refractive index in thedirection in-plane and perpendicular to the in-plane slow axis, andn_(z) represented the refractive index in the direction of thethickness, each measured using light having a wavelength of 550 nm. Thepresent invention has been completed based on the knowledge.

The present invention provides:

-   (1) A liquid crystal display device of an in-plane switching mode    which comprises a pair of polarizers which are a polarizer at an    output side and a polarizer at an incident side and disposed at    relative positions such that absorption axes of the polarizers are    approximately perpendicular to each other and at least optically    anisotropic member (A), optically anisotropic member (B) and a    liquid crystal cell which are disposed between the pair of    polarizers, wherein n_(zA)>n_(yA) and n_(xB)>n_(zB) when, with    respect to optically anisotropic member (A) and optically    anisotropic member (B), refractive indices in a direction of an    in-plane slow axis are represented by n_(xA) and n_(xB),    respectively, refractive indices in a direction in-plane and    perpendicular to the direction of an in-plane slow axis are    represented by n_(yA) and n_(yB), respectively, and refractive    indices in a direction of a thickness are represented by n_(zA) and    n_(zB), respectively, each measured using light having a wavelength    of 550 nm; the in-plane slow axis of optically anisotropic    member (A) and the in-plane slow axis of optically anisotropic    member (B) are disposed at relative positions approximately parallel    or approximately perpendicular to each other; and the in-plane slow    axis of optically anisotropic member (A) and the absorption axis of    a polarizer disposed closer to optically anisotropic member (A) are    disposed at relative positions approximately parallel or    approximately perpendicular to each other;-   (2) The liquid crystal display device described in (1), wherein the    absorption axis of the polarizer at the output side and the in-plane    slow axis of a liquid crystal of the liquid crystal cell under    application of no voltage are disposed at relative positions    parallel to each other, optically anisotropic member (A) and    optically anisotropic member (B) are disposed between the liquid    crystal cell and the polarizer at the incident side, and the    in-plane slow axes of optically anisotropic member (A) and optically    anisotropic member (B) are disposed at relative positions    approximately parallel to each other;-   (3) The liquid crystal display device described in (2), wherein the    in-plane slow axis of optically anisotropic member (B) and the    in-plane slow axis of the liquid crystal of the liquid crystal cell    under application of no voltage are disposed at relative positions    approximately parallel to each other, and optically anisotropic    member (A) is disposed at a position closer to the liquid crystal    cell than optically anisotropic member (B);-   (4) The liquid crystal display device described in (2), wherein the    in-plane slow axis of optically anisotropic member (B) and the    in-plane slow axis of the liquid crystal of the liquid crystal cell    under application of no voltage are disposed at relative positions    approximately perpendicular to each other, and optically anisotropic    member (B) is disposed at a position closer to the liquid crystal    cell than optically anisotropic member (A);-   (5) The liquid crystal display device described in (1), wherein the    absorption axis of the polarizer at the output side and the in-plane    slow axis of a liquid crystal of the liquid crystal cell under    application of no voltage are disposed at relative positions    parallel to each other, optically anisotropic member (A) and    optically anisotropic member (B) are disposed between the liquid    crystal cell and the polarizer at the output side, and the in-plane    slow axes of optically anisotropic member (A) and optically    anisotropic member (B) are disposed at relative positions    approximately parallel to each other;-   (6) The liquid crystal display device described in (5), wherein the    in-plane slow axis of optically anisotropic member (B) and the    in-plane slow axis of the liquid crystal of the liquid crystal cell    under application of no voltage are disposed at relative positions    approximately perpendicular to each other, and optically anisotropic    member (A) is disposed at a position closer to the liquid crystal    cell than optically anisotropic member (B);-   (7) The liquid crystal display device described in (5), wherein the    in-plane slow axis of optically anisotropic member (B) and the    in-plane slow axis of the liquid crystal of the liquid crystal cell    under application of no voltage are disposed at relative positions    approximately parallel to each other, and optically anisotropic    member (B) is disposed at a position closer to the liquid crystal    cell than optically anisotropic member (A);-   (8) The liquid crystal display device described in (1), wherein the    absorption axis of the polarizer at the output side and the in-plane    slow axis of a liquid crystal of the liquid crystal cell under    application of no voltage are disposed at relative positions    parallel to each other, optically anisotropic member (A) and    optically anisotropic member (B) are disposed separately between the    liquid crystal cell and the polarizer at the incident side and    between the liquid crystal cell and the polarizer at the output    side, and the in-plane slow axes of optically anisotropic member (A)    and optically anisotropic member (B) are disposed at relative    positions approximately parallel to each other;-   (9) The liquid crystal display device described in (8), wherein the    in-plane slow axis of optically anisotropic member (A) and the    in-plane slow axis of the liquid crystal of the liquid crystal cell    under application of no voltage are disposed at relative positions    approximately perpendicular, to each other, and optically    anisotropic member (A) is disposed between the liquid crystal cell    and the polarizer at the incident side;-   (10) The liquid crystal display device described in (8), wherein the    in-plane slow axis of optically anisotropic member (A) and the    in-plane slow axis of the liquid crystal of the liquid crystal cell    under application of no voltage are disposed at relative positions    approximately parallel to each other, and optically anisotropic    member (A) is disposed between the liquid crystal cell and the    polarizer at the output side;-   (11) The liquid crystal display device described in any one of (1)    to (10), wherein an absolute value of a difference between n_(xA)    and n_(zA) is 0.003 or smaller, and an absolute value of a    difference between n_(yB) and n_(zB) is 0.003 or smaller; and-   (12) The liquid crystal display device described in any one of (1)    to (ii), wherein optically anisotropic member (A) comprises a layer    selected from following layers (i) to (iii):

(i) A layer comprising a material having a negative value of intrinsicbirefringence,

(ii) A layer comprising discotic liquid crystal molecules or lyotropicliquid crystal molecules,

(iii) A layer comprising a photo-isomerizable substance.

-   (13) A liquid crystal display device which comprises a pair of    polarizers disposed at relative positions such that transmission    axes of the polarizers are approximately perpendicular to each other    and at least optically anisotropic member (A), optically anisotropic    member (B) and a liquid crystal cell which are disposed between the    pair of polarizers, wherein optically anisotropic member (A)    comprises a material layer having a negative value of intrinsic    birefringence, optically anisotropic member (B) comprises a material    layer having a positive value of intrinsic birefringence, the    in-plane slow axis of optically anisotropic member (A) and the    in-plane slow axis of optically anisotropic member (B) are disposed    at relative positions approximately parallel or perpendicular to    each other, and the in-plane slow axis of optically anisotropic    member (A) and a transmission axis of a polarizer disposed closer to    optically anisotropic member (A) are disposed at relative positions    approximately parallel or approximately perpendicular to each other;    and-   (14) A liquid crystal display device which comprises a pair of    polarizers disposed at relative positions such that transmission    axes of the polarizers are approximately perpendicular to each other    and at least optically anisotropic member (A), optically anisotropic    member (B) and a liquid crystal cell which are disposed between the    pair of polarizers, wherein optically anisotropic member (A) is a    member obtained by fixing a liquid crystal compound to a transparent    polymer film in a manner such that the liquid crystal compound is    oriented in a perpendicular direction, optically anisotropic    member (B) is a member obtained by orienting a film comprising a    resin having a positive value of intrinsic birefringence, the    in-plane slow axis of optically anisotropic member (A) and the    in-plane slow axis of optically anisotropic member (B) are disposed    at relative positions approximately parallel or perpendicular to    each other, and the in-plane slow axis of optically anisotropic    member (A) and a transmission axis of a polarizer disposed closer to    optically anisotropic member (A) are disposed at relative positions    approximately parallel or approximately perpendicular to each other;

To summarize the advantages of the present invention, the liquid crystaldisplay device of the present invention exhibits excellentantireflection property, scratch resistance and durability, provides awide angle of field and achieves uniform display of images with greatcontrast at any angle of observation. Therefore, the device can beadvantageously used as a flat panel display having a great area.

In the present invention, the contrast (CR) means contrast expressed by(CR)=Y_(ON)/Y_(OFF), wherein Y_(OFF) represents the luminance during thedark display of a liquid crystal display device, and Y_(ON) representsthe luminance during the bright display of the liquid crystal displaydevice. The greater the value of CR is, the better the visibility is.The bright display means the condition where the brightness of theliquid crystal display is the greatest. The dark display means thecondition where the brightness of the liquid crystal display is thesmallest. In the present invention, the polar angle means the anglebetween the direction of the observation and the direction directly infront of the display when the face of the liquid crystal display isobserved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram exhibiting a preferable arrangement in the liquidcrystal display device of the present invention.

FIG. 2 shows a diagram exhibiting a preferable arrangement in the liquidcrystal display device of the present invention.

FIG. 3 shows a diagram exhibiting an embodiment having arrangement I-1in the liquid crystal display device of the present invention.

FIG. 4 shows a diagram exhibiting an embodiment having arrangement I-2in the liquid crystal display device of the present invention.

FIG. 5 shows a diagram exhibiting an embodiment the arrangement II-1 inthe liquid crystal display device of the present invention.

FIG. 6 shows a diagram exhibiting an embodiment having arrangement II-2in the liquid crystal display device of the present invention.

FIG. 7 shows a diagram exhibiting an embodiment having arrangement III-1in the liquid crystal display device of the present invention.

FIG. 8 shows a diagram exhibiting an embodiment having arrangement III-2in the liquid crystal display device of the present invention.

The numbers in the Figures have the following meanings:

1: A polarizer of the incident side

2: A liquid crystal cell

3: Optically anisotropic member (A)

4: Optically anisotropic member (B)

5: A polarizer at the output side

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

In the liquid crystal display device of the present invention, it ispreferable that n_(zA)>n_(yA) when, with respect to opticallyanisotropic member (A), the refractive index in the direction of anin-plane slow axis is represented by n_(xA), the refractive index in thedirection in-plane and perpendicular to the direction of the in-planeslow axis is represented by n_(yA), and the refractive index in thedirection of the thickness is represented by n_(zA), each measured usinglight having a wavelength of 550 nm. It is more preferable thatn_(zA)−n_(yA) is 0.00001 or greater. It is still more preferable thatn_(zA)−n_(yA) is 0.00003 or greater. When n_(zA)≦n_(yA), there is thepossibility that the contrast of the liquid crystal display device isdecreased from that obtained when the optically anisotropic member isnot disposed.

In the present invention, the absolute value of the difference betweenn_(xA) and n_(zA) is 0.003 or smaller, preferably 0.002 or smaller, morepreferably 0.001 or smaller, still more preferably 0.0008 or smaller,still more preferably 0.0005 or smaller, still more preferably 0.0003 orsmaller and most preferably 0.0001 or smaller. When the refractiveindices do not satisfy the above relation, there is the possibility thatthe contrast of the liquid crystal display device is decreased from thatobtained when the optically anisotropic member is not disposed.

It is preferable that optically anisotropic member (A) used in thepresent invention comprises substances selected from (i) a layercomprising a material having a negative value of intrinsicbirefringence, (ii) a layer comprising discotic liquid crystal moleculesor lyotropic liquid crystal molecules, and (iii) a layer comprising aphoto-isomerizable substance.

(i) A Layer Comprising a Material Having a Negative Value of IntrinsicBirefringence

The material having a negative value of intrinsic birefringence means amaterial exhibiting a property such that, when light is incident on alayer having molecules oriented in the uniaxial order, the refractiveindex with respect to light in the direction of the orientation issmaller than the refractive index with respect to light in the directionperpendicular to the direction of the orientation.

Examples of the material having a negative value of intrinsicbirefringence include vinyl aromatic polymers, polyacrylonitrile-basedpolymers, polymethyl methacrylate-based polymers, cellulose ester-basedpolymers and multi-component copolymers derived from these polymers. Thematerial having a negative value of intrinsic birefringence may be usedsingly or in combination of two or more. Among these materials, vinylaromatic polymers, polyacrylonitrile-based polymers and polymethylmethacrylate-based polymers are preferable, and vinyl aromatic polymersare more preferable since the birefringence is exhibited to a greatdegree.

Examples of the vinyl aromatic polymer include polystyrene andcopolymers of vinyl aromatic monomers such as styrene, α-methylstyrene,o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene,p-aminostyrene, p-carboxystyrene and p-phenylstyrene with other monomerssuch as ethylene, propylene, butadiene, isoprene, (meth)acrylonitrile,α-chloroacrylonitrile, methyl (meth)acrylate, ethyl (meth)acrylate,(meth)acrylic acid, maleic anhydride and vinyl acetate. Among thesepolymers, polystyrene and copolymers of styrene and maleic anhydride arepreferable.

In the present invention, where necessary, conventional additives suchas antioxidants, heat stabilizers, light stabilizers, ultraviolet lightabsorbents, antistatic agents, dispersants, chlorine scavengers, flameretardants, nucleating agents for crystallization, antiblocking agents,anticlouding agents, mold releases, pigments, organic and inorganicfillers, neutralizing agents, lubricants, decomposing agents, metalinactivators, antifouling agents, antibacterial agents, other resins andthermoplastic elastomers may be added to the material having a negativevalue of the intrinsic birefringence as long as the effects of thepresent invention are not adversely affected.

The layer comprising the material having a negative value of theintrinsic birefringence may further comprise other materials. However, alayer comprising the material having a negative value of the intrinsicbirefringence alone is preferable. A laminate having a layer comprisingother materials laminated to at least one face of the layer comprisingthe material having a negative value of the intrinsic birefringence ispreferable. A laminate having layers comprising other materialslaminated to both faces of the layer comprising the material having anegative value of the intrinsic birefringence is more preferable.

The processes for producing the layer comprising the material having anegative value of the intrinsic birefringence and the laminate having alayer comprising other materials laminated to at least one face of thelayer comprising the material having a negative value of the intrinsicbirefringence are not particularly limited. Examples of the processinclude conventional processes such as the flow coating process using asolution, the injection molding process and the melt extrusion process.

It is preferable that the layer comprising the material having anegative value of intrinsic birefringence is an oriented layercomprising the material having a negative value of intrinsicbirefringence. From the standpoint of exhibiting excellent workability,efficiently and easily forming optically anisotropic member (A) andmaintaining stable and uniform phase difference for a long time, it ispreferable that the laminate having a layer comprising other materialslaminated to at least one face of the layer comprising the materialhaving a negative value of the intrinsic birefringence is an orientedlayer. It is more preferable that the laminate having a layer comprisingother materials laminated to both faces of the layer comprising thematerial having a negative value of the intrinsic birefringence is anoriented layer. From the standpoint of efficiently utilizing the phasedifference in the layer comprising the material having a negative valueof intrinsic birefringence, it is preferable that the layer comprisingother materials is a layer having substantially no orientation.

The processes for producing the oriented layer of the layer comprisingthe material having a negative value of intrinsic birefringence and theoriented layer of the laminate having a layer comprising other materialslaminated to at least one face of the layer comprising the materialhaving a negative value of the intrinsic birefringence are notparticularly limited. From the standpoint of uniformly and efficientlycontrolling the refractive index of the optically anisotropic member inthe direction of thickness, the process of stretching the layercomprising the material having a negative value of intrinsicbirefringence is preferable.

From the standpoint of controlling the in-plane refractive index of theoptically anisotropic member, the process of further laminating anotherstretched film to the stretched layer comprising the material having anegative value of intrinsic birefringence is also preferable.

It is preferable that the layer comprising the material having anegative value of intrinsic birefringence has a structure such thatlayers comprising other materials are laminated to both faces of thelayer comprising the material having a negative value of intrinsicbirefringence via a layer of an adhesive resin. Due to this structure,even when the layer comprising the material having a negative value ofintrinsic birefringence has a small strength and stretching of the layeralone is difficult, the stretching becomes possible at a temperaturewhere the birefringence is easily exhibited, and optically anisotropicmember (A) having a uniform phase difference over the entire face of thelayer can be obtained with excellent productivity without fracture.

The processes for stretching the oriented layer of the layer comprisingthe material having a negative value of intrinsic birefringence and theoriented layer of the laminate having a layer comprising other materialslaminated to both faces of the layer comprising the material having anegative value of the intrinsic birefringence are not particularlylimited, and a conventional process can be applied. Examples of theprocess include uniaxial stretching processes such as the process ofuniaxial stretching in the longitudinal direction utilizing thedifference in the circumferential speed of rolls, and the process ofuniaxial stretching in the transverse direction using a tenter;processes of biaxial stretching such as the process of simultaneousstretching comprising longitudinal stretching by increasing the distancebetween fixing clips and transverse stretching by an increase in theangle of opening of guide rails, and the process of successivestretching comprising longitudinal stretching utilizing the differencein the circumferential speed of rolls, followed by transverse stretchingusing a tenter by gripping both end portions by clips; and processes ofoblique stretching such as the process using a tenter stretcher whichcan apply longitudinal or transverse feeding force, tensile force orwinding force at different rightward and leftward speeds, or a tenterstretcher which has the same distance of movement with a fixed angle ofstretching θ or has different distances of movement while longitudinalor transverse feeding force, tensile force or winding force can beapplied at the same rightward and leftward speeds.

As described above, by stretching the layer comprising the materialhaving a negative value of intrinsic birefringence or by stretching thelaminate having a layer comprising other materials laminated to at leastone face of the layer comprising the material having a negative value ofintrinsic birefringence, the refractive index in the directionperpendicular to the direction of stretching of the layer is madegreater and the refractive index in the direction of stretching of thelayer is made smaller. Thus, optically anisotropic substance (A) havinga uniform phase difference can be efficiently and advantageouslyprepared.

(ii-1) A Layer Comprising Discotic Liquid Crystal Molecules

The discotic liquid crystal molecules are described in variousreferences [for example, benzene derivatives described in C. Desrade etal., Mol. Crysr. Liq. Cryst., vol. 71, page 111 (1981); cyclohexanederivatives described in research reports by B. Kohne et al. and Angew.Chem., vol. 96, page 70 (1984); and aza crown-based molecules andphenylacetylene-based macrocycles described in research reports by J. M.Lehn et al., J. Chem. Commun., page 1794 (1985) and research reports byJ. Zhang et al., J. Am. Chem. Sci. vol. 116, page 2655 (1994)]. Ingeneral, the discotic liquid crystal has a structure in which thesemolecules are placed as the mother nucleus and linear alkyl groups andalkoxyl groups and substituted benzoyloxyl group are added assubstituents in the form of linear chains in a radial shape. Specificexamples of the discotic crystal include compounds represented by thefollowing formulae (1) and (2):

In formula (1), R represents one of groups expressed by the followingformulae (i) to (iii):

In formula (2), R represents one of groups expressed by formulae A to F:

It is preferable that the layer comprising the discotic liquid crystalmolecules comprises a layer in which the discotic liquid crystalmolecules are oriented in the direction substantially perpendicular tothe face of the substrate from the standpoint of efficiently and easilyforming optically anisotropic member (A) and maintaining the stable anduniform phase difference for a long time. The substantiallyperpendicular orientation of the discotic liquid crystal molecules meansa condition such that the discotic liquid crystal molecules are arrangedin an orientation at an average oblique angle of 50 to 90° with respectto the face of the substrate. Examples of the substrate include filmsand plates made of glass and resins. From the standpoint of the decreasein the weight, the decrease in the thickness and the efficiency ofproduction, the layer comprising the discotic liquid crystal moleculesmay be a laminate in which the discotic liquid crystal molecules areoriented substantially perpendicularly to the polarizer or opticallyanisotropic member (B) used in the present invention.

The process for producing optically anisotropic member (A) from a layercomprising the discotic liquid crystal molecules is not particularlylimited. A process of laminating the discotic liquid crystal moleculesto a substrate is preferable. From the standpoint of efficient controlof the refractive index in the direction of the thickness of opticallyanisotropic member (A), the process of laminating the discotic liquidcrystal molecules in a manner such that the discotic liquid crystalmolecules are oriented substantially perpendicular to the face of thesubstrate is preferable. Optically anisotropic member (A) can be formedefficiently in accordance with the above process.

As for the process for arranging the discotic liquid crystal moleculesin the perpendicular direction, this arrangement can be obtained bycoating a film for perpendicular orientation with a coating fluidcomprising the discotic liquid crystal molecules or a combination of thediscotic liquid crystal molecules, a polymerization initiator describedlater and other additives, followed by fixing the substances in thecoating fluid to the film, or by coating a film for perpendicularorientation with the coating fluid, followed by fixing the substances inthe coating fluid to the film, then by removing the film forperpendicular orientation and laminating the remaining layer comprisingthe discotic liquid crystal molecules to a substrate.

Examples of the solvent used for preparation of the coating fluidinclude water and organic solvents. Examples of the organic solventinclude amides such as N,N-dimethylformamide; sulfoxides such asdimethyl sulfoxide; heterocyclic compounds such as pyridine;hydrocarbons such as benzene and hexane; alkyl halides such aschloroform and dichloromethane; esters such as methyl acetate and butylacetate; ketones such as acetone and methyl ethyl ketone; and etherssuch as tetrahydrofuran and 1,2-dimethoxyethane. Two or more organicsolvents may be used in combination.

The coating with the coating fluid can be conducted in accordance with aconventional process such as the extrusion coating process, the directgravure coating process, the reverse gravure coating process and the diecoating process.

The film for perpendicular orientation means a film having a smallsurface energy such that liquid crystal molecules can be orientedperpendicularly. The film for perpendicular orientation is, in general,formed with a polymer. In particular, from the standpoint of decreasingthe surface energy of the film for perpendicular orientation, a polymerin which fluorine atom or a hydrocarbon group having 10 or more carbonatoms is introduced as a side chain of the polymer is preferable. Thehydrocarbon group is an aliphatic group, an aromatic group or acombination of these groups. It is preferable that the main chain of thepolymer has the structure of a polyimide or polyvinyl alcohol.

The degree of polymerization of the polymer used for the film forperpendicular orientation is preferably 200 to 5,000 and more preferably300 to 3,000. The molecular weight of the polymer is preferably 9,000 to200,000 and more preferably 13,000 to 130,000. Two or more polymers maybe used in combination.

The film for perpendicular orientation can be formed by coating asubstrate with the above polymer used for the film for perpendicularorientation. It is preferable that the film for perpendicularorientation is subjected to the rubbing treatment. The rubbing treatmentcan be conducted by rubbing the surface of the film having the polymerwith paper or a cloth several times in a specific direction.

The perpendicularly oriented discotic liquid crystal molecules are fixedwhile the oriented condition is maintained. It is preferable that thefixing is conducted by polymerization. The liquid crystal moleculesfixed in the perpendicularly oriented condition can maintain theoriented condition without the film for perpendicular orientation.

Examples of the process for the polymerization include the thermalpolymerization using a thermal polymerization initiator and thephoto-polymerization using a photopolymerization initiator. Thephoto-polymerization is preferable among the polymerization processes.

Examples of the photopolymerization initiator include α-carbonylcompounds (described in the specifications of the U.S. Pat. Nos.2,367,661 and 2,367,670), acyloin ethers (described in the specificationof the U.S. Pat. No. 2,448,828), aromatic acyloin compounds substitutedwith α-hydrocarbon (described in the specification of the U.S. Pat. No.2,722,512), polynuclear quinone compounds (described in thespecifications of the U.S. Pat. Nos. 3,046,127 and 2,951,758),combinations of triarylimidazole dimers and p-aminophenyl ketones(described in the specification of the U.S. Pat. No. 3,549,367),acridine and phenazine compounds (described in the specifications ofJapanese Patent Application Laid-Open No. Showa 60(1985)-105667 and theU.S. Pat. No. 4,239,850) and oxadiazole compounds (described in thespecification of the U.S. Pat. No. 4,212,970).

As described above, due to the formation of the layer in which thediscotic liquid crystal molecules are perpendicularly oriented, therefractive index of this layer in the direction substantially parallelto the face of the disk of the perpendicularly oriented discotic liquidcrystal molecules is increased, and the refractive index in thedirection of the normal of the face of the disk is decreased. Therefore,optically anisotropic member (A) having a uniform phase difference canbe formed efficiently and advantageously.

(i-2) Layer Comprising Lyotropic Liquid Crystal Molecules

The lyotropic liquid crystal molecule means a molecule exhibiting theliquid crystal property when the molecule is dissolved into a specificsolvent in a concentration in a specific range (refer to Ekisho Binran(Handbook of Liquid Crystals), published by Maruzen Co., Ltd., page 3 orelse). Specific examples include macromolecular lyotropic liquid crystalmolecules obtained by dissolving a macromolecule having the main chainhaving a rod-like skeleton structure such as cellulose derivatives,polypeptides and nucleic acids; amphiphilic lyotropic liquid crystalmolecules comprising a concentrated aqueous solution of an amphiphiliclow molecular weight compound; and chromonic liquid crystal moleculescomprising a solution of a low molecular weight compound having anaromatic ring provided with solubility in water, which are described inJapanese Patent Application Laid-Open No. Heisei 10(1998)-333145 andMol. Cryst., Liq. Cryst., 1993, Vol. 225, 293-310.

It is preferable that the lyotropic liquid crystal molecules used in thepresent invention are characterized by that the molecules are orientedin a specific direction under shearing force. It is also preferable thatthe lyotropic liquid crystal molecules used in the present inventionsubstantially do not have absorption in the region of visible light.Specific examples of the lyotropic liquid crystal molecule includecompounds expressed by the following formulae (3) and (4):

It is preferable that the layer comprising the lyotropic liquid crystalcomprises a layer in which lyotropic liquid crystal molecules areoriented in the direction substantially perpendicular to the face of thesubstrate from the standpoint of efficiently and easily formingoptically anisotropic member (A) and maintaining the stable and uniformphase difference for a long time. The substantially perpendicularorientation of the lyotropic liquid crystal molecules means a conditionsuch that the lyotropic liquid crystal molecules are arranged in anorientation at an average oblique angle of 50 to 90° with respect to theface of the substrate. Examples of the substrate include films andplates made of glass and resins.

The process for producing optically anisotropic member (A) from a layercomprising the lyotropic liquid crystal molecules is not particularlylimited. A process of laminating the lyotropic liquid crystal moleculesto a substrate is preferable. From the standpoint of efficient controlof the refractive index in the direction of the thickness of opticallyanisotropic member (A), the process of laminating the lyotropic liquidcrystal molecules in a manner such that the lyotropic liquid crystalmolecules are oriented substantially perpendicular to the face of thesubstrate under shearing force is preferable. Optically anisotropicsubstance (A) can be formed efficiently in accordance with the aboveprocess.

Examples of the process for perpendicularly orienting the lyotropicliquid crystal molecules under shearing force include a process ofcoating a substrate with a coating fluid comprising the lyotropic liquidcrystal molecules or a combination of the discotic liquid crystalmolecules, a polymerization initiator described later and otheradditives, followed by fixing the substances in the coating fluid to thefilm. It is preferable in the treatment for the orientation that a filmfor perpendicular orientation is not used so that the efficiency ofproduction is made excellent, the decreases in the weight and thethickness can be achieved, damages to the substrate can be prevented,and the coating can be achieved with a uniform thickness.

Examples of the solvent used for preparation of the coating fluidinclude water and organic solvents. Examples of the organic solventinclude amides such as N,N-dimethylformamide; sulfoxides such asdimethyl sulfoxide; heterocyclic compounds such as pyridine;hydrocarbons such as benzene and hexane; alkyl halides such aschloroform and dichloromethane; esters such as methyl acetate and butylacetate; ketones such as acetone and methyl ethyl ketone; and etherssuch as tetrahydrofuran and 1,2-dimethoxyethane. Two or more organicsolvents may be used in combination.

The concentration of the solution comprising the lyotropic liquidcrystal molecules is not particularly limited as long as the moleculesused for the layer of optically anisotropic member (A) exhibit theliquid crystal property. The liquid crystal molecules are dissolved inthe solvent in an amount preferably in the range of 0.0001 to 100 partsby weight and more preferably in the range of 0.0001 to 1 part byweight.

Where necessary, the solution comprising the lyotropic liquid crystalmolecules may comprise conventional additives such as polymerizationinitiators, antioxidants, heat stabilizers, light stabilizers,ultraviolet light absorbents, antistatic agents, dispersants, chlorinescavengers, flame retardants, nucleating agents for crystallization,antiblocking agents, anticlouding agents, mold releases, pigments,organic and inorganic fillers, neutralizing agents, lubricants,decomposing agents, metal inactivators, antifouling agents,plasticizers, adhesives, anti-bacterial agents, other resins andthermoplastic elastomers as long as the effects of the present inventionare not adversely affected. The additive is added to the solutioncomprising the lyotropic liquid crystal molecules in an amount, ingeneral, in the range of 0 to 5 parts by weight and preferably in therange of 0 to 3 parts by weight.

The coating with the solution comprising the lyotropic liquid crystalmolecules can be conducted in accordance with a conventional processsuch as the extrusion coating process, the direct gravure coatingprocess, the reverse gravure coating process and the die coatingprocess.

The lyotropic liquid crystal molecules perpendicularly oriented undershearing force are fixed while the oriented condition is maintained.Examples of the process for the fixing include removal of the solvent bydrying, polymerization and a combination of these processes. Examples ofthe polymerization include the thermal polymerization using a thermalpolymerization initiator and the photopolymerization using aphoto-polymerization initiator.

As described above, due to the formation of a layer in which thelyotropic liquid crystal molecules are perpendicularly oriented, therefractive index in the direction substantially perpendicular to thedirection of shearing of the lyotropic liquid crystal moleculesperpendicularly oriented under shearing force is increased, and therefractive index in the direction of the shearing is decreased.Therefore, optically anisotropic member (A) having a uniform phasedifference can be formed efficiently and advantageously.

(iii) A Layer Comprising a Photo-Isomerizable Substance

The photo-isomerizable substance means a compound which is stericallyisomerized or structurally isomerized by light and, preferably, isfurther isomerized in the reverse direction by light having a differentwavelength or by heat. Among the above compound, in general, many ofcompounds which change the structure accompanied with a change in thecolor tone in the visible region are known as the photochromiccompounds. Examples of the photochromic compounds includeazobenzene-based compounds, benzaldoxime-based compounds,azomethine-based compounds, stilbene-based compounds, spiropyrane-basedcompounds, spirooxazine-based compounds, fulgide-based compounds,diarylethene-based compounds, cinnamic acid-based compounds,retinal-based compounds and hemithioindigo-based compounds.

The above photo-isomerizable substance, which is a compound having aphoto-isomerizable functional group (such as azo group and innerolefins), may be a low molecular weight compound or a polymer. When thephoto-isomerizable substance is a polymer, the same function can beexhibited when the photo-isomerizable group is either in the main chainor in a side chain. The polymer may be a homopolymer or a copolymer. Asfor the relative amounts of monomer components in the copolymer, asuitable value can be used so that the properties of the copolymer suchas the ability of photo-isomerization and Tg are suitably adjusted. Thecompound having the photo-isomerizable group may be a liquid crystalcompound, at the same time. In other words, the liquid crystal compoundmay have a photo-isomerizable functional group in the molecule. Thephoto-isomerizable substance is specifically described in Kobunshi, 41(12), (1992), page 884; “Chromic Materials and Application” (ed. byCMC), page 221; “Mechanochemistry” (ed. by Maruzen), page 21; and“Kobunshi Ronbunshu”, vol. 147, No. 10 (1991), page 771. As a specificexample of the photo-isomerizable substance, a compound expressed byformula (5) is shown in the following.

It is preferable that the layer comprising the photo-isomerizablesubstance is a layer comprising the photo-isomerizable substance whichhas been isomerized into a specific isomer from the standpoint ofefficiently and easily forming optically anisotropic member (A) andmaintaining the stable and uniform phase difference.

The process for producing optically anisotropic member (A) from a layercomprising the photo-isomerizable substance is not particularly limited.A process of coating a substrate with a solution comprising thephoto-isomerizable substance to form a film, followed by irradiationwith linearly polarized light via a drying step is preferable. Theprocess comprising irradiation of the face of the film with linearlypolarized light in the direction perpendicular to the face is morepreferable. Optically anisotropic substance (A) can be formedefficiently in accordance with the above process. Examples of thesubstrate include films and plates made of glass and resins.

The solvent used for preparation of the solution comprising thephoto-isomerizable substance is not particularly limited. Examples ofthe solvent include organic solvents such as methylene chloride,acetone, methanol and methyl ethyl ketone. The concentration of thecoating fluid is not particularly limited and is selected so thatviscosity suitable for the coating can be obtained. The concentration ispreferably 1 to 50%. As the process for the coating, a conventionalcoating process such as the bar coating process and the roll coatingprocess can be utilized.

For irradiation with the linearly polarized light, the irradiation canbe conducted when the coating layer has been approximately dried. Theapproximately dried condition may be considered to be the condition inwhich the residual amount of the solvent in the coating layer is 10% byweight or less. It is preferable that the temperature of the irradiationwith the linearly polarized light is in the range of Tg−50° C. to Tg+30°C. although the optimum temperature is different depending on theresidual amount of the solvent. The source of the polarized light is notparticularly limited. A mercury lamp or a halogen lamp can beadvantageously used.

As described above, due to the irradiation of the layer comprising thephoto-isomerizable substance with the linearly polarized light, therefractive index in the direction substantially perpendicular to thedirection of the polarization axis of the light used for the irradiationis increased, and the refractive index in the direction of thepolarization axis of the light used for the irradiation is decreased.Therefore, optically anisotropic member (A) having a uniform phasedifference can be formed efficiently and advantageously.

In the liquid crystal display device of the present invention, it ispreferable that n_(xB)>n_(zB) when, with respect to opticallyanisotropic member (B), the refractive index in the direction of anin-plane slow axis is represented by n_(xB), the refractive index in thedirection in-plane and perpendicular to the direction of the in-planeslow axis is represented by n_(yB), and the refractive index in thedirection of the thickness is represented by n_(zB), each measured usinglight having a wavelength of 550 nm. It is more preferable thatn_(xB)−n_(zB) is 0.00001 or greater. It is still more preferable thatn_(zB)−n_(zB) is 0.00003 or greater. When n_(x)≦n_(zB), there is thepossibility that the contrast of the liquid crystal display device isdecreased from that obtained when the optically anisotropic member isnot disposed.

In the present invention, the absolute value of the difference betweenn_(yB) and n_(zB) is 0.003 or smaller, preferably 0.002 or smaller, morepreferably 0.001 or smaller, still more preferably 0.0008 or smaller,still more preferably 0.0005 or smaller, still more preferably 0.0003 orsmaller and most preferably 0.0001 or smaller. When the refractiveindices do not satisfy the above relations, there is the possibilitythat the contrast of the liquid crystal display device is decreased fromthat obtained when the optically anisotropic member is not disposed.

Optical anisotropic member (B) used in the present invention is notparticularly limited as long as the optically anisotropic membersatisfies the relation of n_(xB)>n_(zB). It is preferable that opticallyanisotropic member (B) comprises a layer comprising a material having apositive value of intrinsic birefringence. The material having apositive value of intrinsic birefringence means a material exhibiting aproperty such that, when light is incident on a layer having moleculesoriented in a uniaxial order, a refractive index with respect to lightin the direction of the orientation is greater than the refractive indexwith respect to light in the direction perpendicular to the direction ofthe orientation.

Examples of the material having a positive value of intrinsicbirefringence include polymers having an alicyclic structure, polyolefinpolymers, polycarbonate polymers, polyester polymers such aspolyethylene terephthalate, polyvinyl chloride polymers, polysulfonepolymers, polyether sulfone polymers, polyarylate polymers, acetatepolymers such as triacetylcellulose and liquid crystalline resins. Amongthese materials, polymers having an alicyclic structure are preferable.

Examples of the polymer having an alicyclic structure includenorbornene-based polymers, polymers based on cyclic olefins having asingle ring, cyclic conjugate diene-based polymers, polymers of vinylalicyclic hydrocarbons and hydrogenation products of these polymers.Among these polymers, norbornene-based polymers are preferable from thestandpoint of transparency and the molding property.

Examples of the norbornene-based polymer include ring-opening polymersof monomers having a norbornene structure, ring-opening copolymers ofmonomers having a norbornene structure with other monomerscopolymerizable with the monomers having the norbornene structure inaccordance with the ring-opening copolymerization, hydrogenationproducts of these polymers, addition polymers of monomers having anorbornene structure, addition-type copolymers of monomers having anorbornene structure with other monomers copolymerizable with themonomers having a norbornene structure and hydrogenation products ofthese polymers. Among these polymers, hydrogenation products ofring-opening (co)polymers of monomers having a norbornene structure arepreferable from the standpoint of transparency, the molding property,heat resistance, small moisture absorption, dimensional stability andlight weight.

In the present invention, where necessary, the additives described forthe material having a negative intrinsic birefringence may be added tothe layer comprising the material having a positive value of intrinsicbirefringence as long as the effects of the present invention are notadversely affected.

The layer comprising the material having a positive value of theintrinsic birefringence may further comprise other materials. However, alayer comprising the material having a positive value of the intrinsicbirefringence alone is preferable.

The process for producing the layer comprising the material having apositive value of the intrinsic birefringence is not particularlylimited. Examples of the process include conventional processes such asthe flow coating process using a solution, the injection molding processand the melt extrusion process.

It is preferable that the layer comprising the material having apositive value of intrinsic birefringence is an oriented layercomprising the material having a positive value of intrinsicbirefringence from the standpoint of easily and efficiently producingoptically anisotropic member (B) and maintaining the stable and uniformphase difference for a long time.

The process for producing the oriented layer of the layer comprising thematerial having a positive value of intrinsic birefringence is notparticularly limited. From the standpoint of uniformly and efficientlycontrolling the in-plane refractive index of the optically anisotropicmember, the process of stretching the layer comprising the materialhaving a positive value of intrinsic birefringence is preferable.

The process for stretching the layer comprising the material having apositive value of intrinsic birefringence is not particularly limited,and a conventional process can be applied. Specifically, the processesdescribed for the material having a negative value of intrinsicbirefringence can be applied.

As described above, by stretching the layer comprising the materialhaving a positive value of intrinsic birefringence, the refractive indexin the direction perpendicular to the direction of stretching of thelayer is made greater and the refractive index in the direction ofstretching of the layer is made smaller. Thus, optically anisotropicsubstance (B) having a uniform phase difference can be efficiently andadvantageously prepared.

In the liquid crystal display device of the present invention, thecontent of the residual volatile components in optically anisotropicmember (A) and optically anisotropic member (B) is preferably 0.1% byweight or smaller and more preferably 0.01% by weight or smaller. Whenthe contents of residual volatile components in both of opticallyanisotropic member (A) and optically anisotropic member (B) exceed 0.1%by weight, there is the possibility that the phase difference is notuniform since the volatile components are discharged to the outsideduring the use, and internal stress is generated due to a dimensionalchange formed in optically anisotropic member (A) or opticallyanisotropic member (B). When the contents of residual volatilecomponents in both of optically anisotropic member (A) and opticallyanisotropic member (B) in the liquid crystal display device of thepresent invention are within the above range, the optical propertyexhibits excellent stability in that the liquid display device shows nodecrease in the contrast of displayed images or uneven display under anyenvironment even after the use for a long time.

The volatile components are substances contained in the opticallyanisotropic members in minute amounts and having molecular weights of200 or smaller, such as residual monomers and solvents. The content ofthe volatile components can be determined as the total of the amounts ofthe substances having a molecular weight of 200 or smaller in theanalysis of the optically anisotropic member in accordance with the gaschromatography.

The liquid crystal display device of the present invention is a liquidcrystal display device of an in-plane switching mode which comprises apair of polarizers which are a polarizer at an output side and apolarizer at an incident side and disposed at relative positions suchthat absorption axes of the polarizers are approximately perpendicularto each other and at least optically anisotropic member (A), opticallyanisotropic member (B) and a liquid crystal cell which are disposedbetween the pair of polarizers, wherein the in-plane slow axis ofoptically anisotropic member (A) and the in-plane slow axis of opticallyanisotropic member (B) are disposed at relative positions approximatelyparallel or approximately perpendicular to each other; and the in-planeslow axis of optically anisotropic member (A) and the absorption axis ofa polarizer disposed closer to optically anisotropic member (A) aredisposed at relative positions approximately parallel or approximatelyperpendicular to each other.

In the present invention, the angle between two axes is defined as theangle between a plane having one of the axes as the normal and anotherplane having the other of the axes as the normal, wherein the smallerangle is selected. In the present invention, that two axes are disposedat relative positions approximately parallel to each other means thatthe angle between the two axes is 0 to 3°, and that two axes aredisposed at relative positions approximately perpendicular to each othermeans that the angle between the two axes is 87 to 90°.

It is preferable that optically anisotropic member (A) and opticallyanisotropic member (B) used in the present invention have uniformoptical properties. It is more referable that the dispersion of thein-plane retardation is 10 nm or smaller, still more preferably 5 nm orsmaller and most preferably 2 nm or smaller. When the dispersion of thein-plane retardation is within the above range, the quality of displayof the liquid crystal display device of the present invention can bemade excellent. The dispersion of the in-plane retardation means thedifference between the maximum value and the minimum value of thein-plane retardation when the in-plane retardation is measured over theentire face of the optically anisotropic members in the condition suchthat the incident angle of light is 0°, i.e., when the incident lightand the surfaces of optically anisotropic member (A) and opticallyanisotropic member (B) used in the present invention are perpendicularto each other.

The in-plane switching (IPS) mode, which is one of the modes of theliquid crystal display device of the present invention, uses liquidcrystal molecules homogenously oriented in the horizontal direction andtwo polarizers having transmission axes disposed at relative positionsperpendicular to each other, one transmission axis being in the verticaldirection and the other transmission axis being in the horizontaldirection with respect to the front face of the display. Therefore, thesufficient contrast can be obtained since the two transmission axes arein such relative positions that the two transmission axes are seenperpendicularly when the face of the display is observed at ahorizontally or vertically oblique angle and, moreover, thehomogeneously oriented liquid crystal layer shows little birefringenceunlike liquid crystal layers of the twisted mode. However, when the faceof the display is observed obliquely at the angle of 45°, the anglebetween the transmission axes of the two polarizers shifts from 90°, andleak of light takes place due to birefringence of the transmitted light.Therefore, the sufficiently dark color is not obtained, and the contrastdecreases. To overcome this drawback, optically anisotropic member (A)and optically anisotropic substance (B) are disposed between twopolarizers of the liquid crystal display device of the in-planeswitching mode in a manner such that the in-plane slow axis of opticallyanisotropic member (A) and the in-plane slow axis of opticallyanisotropic member (B) are disposed at relative positions approximatelyparallel to each other, and the in-plane slow axis of opticallyanisotropic member (A) and the transmission axis of the polarizerdisposed closer to optically anisotropic member (A) are disposed atrelative positions approximately parallel or approximately perpendicularto each other. Due to this arrangement of relative positions, the phasedifference formed by the liquid crystal in the liquid crystal cell iscompensated, and compensation for the angle of field of the polarizer isalso achieved. Due to the above effect, the phase difference formed bythe transmitted light is effectively compensated to prevent the leak oflight, and excellent contrast can be obtained in observation at any ofthe entire angle. This effect is considered to be exhibited also in thecases of liquid crystal display devices of other modes. In particular,the effect is remarkable in the case of the IPS mode.

In the liquid display device of the present invention, a suitablepolarizer which is obtained from a film comprising a suitableconventional vinyl alcohol-based polymer such as polyvinyl alcohol andpolyvinyl alcohol with a partial formal treatment after suitabletreatments such as the dying with dichroic substances (such as iodineand dichroic dyes), the stretching treatment and the crosslinkingtreatment in a suitable order in accordance with suitable processes andtransmits linearly polarized light on incidence of natural light, can beused. In particular, a polarizer exhibiting excellent transmission oflight and degree of polarization is preferable. In general, thethickness of the polarizer is 5 to 80 μm. However, the thickness is notlimited to this range.

In general, protective films are attached to both faces of thepolarizer, and the obtained laminate is used as a polarizer plate.

As the protective film in the polarizer, a suitable transparent film canbe used. In particular, films comprising a polymer exhibiting excellenttransparency, mechanical strength, heat stability and property ofshielding moisture are preferable. Examples of the polymer includepolymers having an alicyclic structure, polyolefin polymers,polycarbonate polymers, polyester polymers such as polyethyleneterephthalate, polyvinyl chloride polymers, polystyrene polymers,polyacrylonitrile polymers, polysulfone polymers, polyether sulfonepolymers, polyarylate polymers, acetate polymers such astriacetylcellulose and copolymers of (meth)acrylic acid esters and vinylaromatic compounds. Among these polymers, triacetylcellulose,polyethylene terephthalate and polymer resins having an alicyclicstructure are preferable from the standpoint of transparency and lightweight, and polyethylene terephthalate and polymer resins having analicyclic structure are more preferable from the standpoint ofdimensional stability and control of the thickness of the film. Theoptically anisotropic member used in the present invention can work alsoas the protective film for the polarizer so that the thickness of theliquid crystal display device can be decreased.

In the present invention, when the optically anisotropic member and thepolarizer are in contact with each other, the optically anisotropicmember may replace the protective film of the polarizer described aboveand can be attached to the polarizer using a suitable means such as anadhesive or a pressure-sensitive adhesive.

Examples of the adhesive and the pressure-sensitive adhesive includeadhesives and pressure-sensitive adhesives based on acrylic polymers,silicones, polyesters, polyurethanes, polyethers and rubbers. Amongthese materials, acrylic adhesives and pressure-sensitive adhesives arepreferable from the standpoint of heat resistance and transparency.

As the process for lamination, a conventional process for lamination canbe used. Examples of the process for lamination include the process oflaminating the optically anisotropic member and the polarizer which areeach cut into a desired size, and the process of laminating long sheetsof the optically anisotropic member and the polarizer in accordance withthe roll-to-roll process.

Examples of the polymer resin having an alicyclic structure includenorbornene-based polymers, polymers based on cyclic olefins having asingle ring, cyclic conjugate diene-based polymers, vinyl alicyclichydrocarbon polymers and hydrogenation products of these polymers. Amongthese polymers, norbornene-based polymers are preferable from thestandpoint of transparency and the molding property.

Examples of the norbornene-based polymer include ring-opening polymersof norbornene-based monomers, ring-opening copolymers ofnorbornene-based monomers with other monomers copolymerizable with thenorbornene-based monomers in accordance with the ring-openingcopolymerization, hydrogenation products of these polymers, additionpolymers of norbornene-based monomers and addition-type copolymers ofnorbornene-based monomers with other monomers copolymerizable with thenorbornene-based monomers. Among these polymers, hydrogenation productsof ring-opening (co)polymers of norbornene-based monomers are preferablefrom the standpoint of transparency.

The polymer resin having an alicyclic structure can be selected fromconventional polymers disclosed, for example, in Japanese PatentApplication Laid-Open No. 2002-321302.

The protective film for the polarizer at the side of vision in theliquid crystal display device of the present invention can be preparedby laminating a hard coat layer and a low refractive index layer in thisorder.

The hard coat layer is a layer having a great hardness of the surface.Specifically, the hard coat layer is a layer having a hardness of “HB”or harder measured in accordance with the test method of pencil hardness(using a glass plate as the test plate) described in Japanese IndustrialStandard K 5600-5-4. It is preferable that the hard coat layer has agreat refractive index. When the hard coat layer has a great refractiveindex, formation of images due to outside light can be prevented, and apolarizer exhibiting excellent scratch resistance and property forpreventing fouling can be prepared. The average thickness of the hardcoat layer is not particularly limited. The thickness is, in general,0.5 to 30 μm and preferably 3 to 15 μm. The great refractive index meansa refractive index greater than the refractive index of the lowrefractive index layer which will be laminated later and is preferably1.55 or greater. The refractive index can be obtained by using, forexample, a conventional spectro-elipsometer.

The material for constituting the hard coat layer is not particularlylimited as long as the material exhibits a hardness of “HB” or hardermeasured in accordance with the test method of pencil hardness (using aglass plate as the test plate) described in Japanese Industrial StandardK 5600-5-4.

Examples of the above material include organic hard coat materials suchas organic silicone-based materials, melamine-based materials,epoxy-based materials, acrylic materials and urethane acrylate-basedmaterials; and inorganic hard coat materials such as silicondioxide-based materials. Among these materials, urethane acrylate-basedhard coat materials and polyfunctional acrylate-based hard coatmaterials are preferable from the standpoint of excellent adhesiveability and productivity.

In the present invention, it is preferable that the hard coat layer hasa refractive index of 1.5 or greater, more preferably 1.53 or greaterand most preferably 1.55 or greater. When the refractive index of thehard coat layer is in this range, an excellent property of preventingreflection in a wide band range is exhibited, the design of the lowrefractive index layer to be laminated on the hard coat layer isfacilitated, and a laminate film for optical applications exhibitingexcellent scratch resistance can be obtained.

It is preferable that the hard coat layer further comprises particles ofan inorganic oxide.

By adding particles of an inorganic oxide, a hard coat layer exhibitingexcellent scratch resistance and having a refractive index of 1.55 orgreater can be easily formed.

As the particles of an inorganic oxide which can be used for the hardcoat layer, particles having a great refractive index are preferable.Specifically, particles of an inorganic oxide having a refractive indexof 1.6 or greater are preferable, and particles of an inorganic oxidehaving a refractive index of 1.6 to 2.3 are more preferable.

Examples of the particles of an inorganic oxide having a greatrefractive index include particles of titania (titanium oxide), zirconia(zirconium oxide), zinc oxide, tin oxide, cerium oxide, antimonypentaoxide, indium oxide doped with tin (ITO), tin oxide doped withantimony (ATO), tin oxide doped with phosphorus (PTO), indium oxidedoped with zinc (IZO), zinc oxide doped with aluminum (AZO) and tinoxide doped with fluorine (FTO).

Among these particles, particles of antimony pentaoxide are suitable asa component for adjusting the refractive index due to the greatrefractive index and excellent balance between electric conductivity andtransparency.

The low refractive index layer is a layer having a refractive indexsmaller than that of the hard coat layer. The refractive index of thelow refractive index layer is preferably 1.36 or smaller, morepreferably 1.35 to 1.25, and most preferably 1.34 to 1.30. When therefractive index is within the above range, a protective film for apolarizer plate exhibiting excellent balance between visibility, scratchresistance and strength can be formed. The thickness of the lowrefractive index layer is preferably 10 to 1,000 nm and more preferably30 to 500 nm.

The material constituting the low refractive index layer is notparticularly limited as long as the layer having a refractive indexwithin the above range can be formed. Aero gel is preferable since thecontrol of the refractive index is easy and water resistance isexcellent.

The aero gel is a transparent porous substance having minute poresdispersed in a matrix. Most of the pores have a size of 200 nm orsmaller. The content of the pore is, in general, 10% by volume orgreater and 60% by volume or smaller and preferably 20% by volume orgreater and 40% by volume or smaller.

Examples of the aero gel having dispersed minute pores include silicaaero gel and porous substances containing hollow particles dispersed ina matrix.

The aero gel can be produced by supercritical drying of a gel-formcompound which is obtained by polymerization of an alkoxysilane withhydrolysis, has a skeleton structure of silica and is in the swollencondition, as disclosed in the U.S. Pat. Nos. 4,402,927, 4,432,956 and4,610,863. The supercritical drying can be conducted, for example, byreplacing a portion or the entire amount of a solvent in a gel-formcompound with a drying fluid such as carbon dioxide and an alcohol,followed by bringing the resultant compound into a supercriticalcondition and removing the drying fluid (as a gas) which has changedinto the gas phase from the supercritical condition. The silica aero gelmay be produced using sodium silicate as the raw material in a mannerdescribed above as disclosed in the U.S. Pat. Nos. 5,137,279 and5,124,364. The refractive index of the silica aero gel can be changed asdesired by adjusting relative amounts of raw materials.

Examples of the porous substances containing hollow particles dispersedin a matrix include porous substances in which hollow fine particleshaving pores at the inside are dispersed in a binder resin as disclosedin Japanese Patent Application Laid-Open Nos. 2001-233611 and2003-149642.

The binder resin can be selected from resins satisfying requirementssuch as dispersion of hollow fine particles, transparency of the poroussubstance and strength of the porous substance. Examples of the binderresin include conventional resins used for coating such as polyesterresins, acrylic resins, urethane resins, vinyl chloride resins, epoxyresins, melamine resins, fluororesins, silicone resins, butyral resins,phenol resins, vinyl acetate resins, ultraviolet light curable resins,electron beam curable resins, emulsion resins, water-soluble resins,hydrophilic resins, mixtures of these resins and copolymers and modifiedsubstances of these resins; and hydrolyzable organic silicon compoundssuch as alkoxysilanes and hydrolysis products thereof.

Among the above resins, acrylic resins, epoxy resins, urethane resins,silicone resins, hydrolyzable organic silicon compounds such asalkoxysilanes and hydrolysis products thereof are preferable from thestandpoint of dispersion of the fine particles and strength of theporous substance.

The hydrolyzable organic silicon compound such as alkoxysilanes andhydrolysis products thereof are formed from one or more compoundsselected from the group consisting of compounds (a) and products (b) and(c) shown in the following:

(a) Compounds represented by formula (6):SiX₄  (6)

(b) Products of partial hydrolysis of at least one of compoundsrepresented by formula (6)

(c) Products of complete hydrolysis of at least one of compoundsrepresented by formula (6)

and have a bond represented by —(O—Si)_(m)—O— (m representing a naturalnumber) in the molecule.

The hollow fine particles are not particularly limited as long as theparticles are fine particles of an inorganic compound. Inorganic fineparticles having a hollow formed at the inside of an outer shell arepreferable, and silica-based hollow fine particles are more preferable.As the inorganic hollow fine particles, particles having (A) a singlelayer of an inorganic oxide, (B) a single layer of a complex oxidecomprising inorganic oxides of different types and (C) a double layercomprising layers (A) and (B) described above can be used.

The outer shell may be a porous shell having fine open pores or a closedshell having no open pores so that the hollow at the inside is shieldedfrom the outside of the shell. As the outer shell, a coating layercomprising a plurality of coating layers of an inorganic oxide whichcomprises an inner first coating layer of an inorganic oxide and anouter second coating layer of an inorganic oxide is preferable. Bydisposing the outer second coating layer of an inorganic oxide at theoutside, the outer shell can be made dense by closing pores of the outershell, or inorganic hollow fine particles having a hollow completelyshielded from the outside can be obtained. It is preferable that anorganic silicon compound having fluorine atom is used for forming theouter second coating layer comprising an inorganic oxide since therefractive index can be decreased, dispersion into organic solvents canbe improved, and the property of preventing fouling can be provided.Examples of the organic silicon compound having fluorine atom include3,3,3-trifluoropropyltrimethoxy-silane,methyl-3,3,3-trifluoropropyldimethoxysilane,heptadecafluoro-decylmethyldimethoxysilane,heptadecafluorodecyltrichlorosilane,heptadecafluorodecyltrimethoxysilane, trifluoropropyltrimethoxysilaneand tridecafluorooctyltrimethoxysilane.

The thickness of the outer shell is preferably in the range of 1 to 50nm and more preferably in the range of 5 to 20 nm. When the thickness ofthe outer shell is smaller than 1 nm, there is the possibility that theinorganic hollow fine particles cannot maintain the prescribed shape.When the thickness of the outer shell exceeds 50 nm, the hollow at theinside of the inorganic hollow particles is small. As the result, thereis the possibility that the relative volume of the hollow is decreased,and the decrease in the refractive index is insufficient.

The average diameter of the inorganic fine particles is not particularlylimited. The average diameter is preferably 5 to 2,000 nm and morepreferably 20 to 100 nm. When the average diameter is smaller than 5 nm,the effect of the hollows to decrease the refractive index is small.When the average diameter exceeds 2,000 nm, transparency extremelydeteriorates, and the contribution of diffusion and reflectionincreases. The average diameter of the fine particles is thenumber-average diameter obtained by the observation using a transmissionelectron microscope.

The protective film for the polarizer at the side of vision has amaximum reflectance of light having wavelengths in the range of 430 to700 nm of preferably 1.4% or smaller and more preferably 1.3% or smallerat an incident angle of 5°. The reflectance of light having a wavelengthof 550 nm is preferably 0.7% or smaller and more preferably 0.6% orsmaller at an incident angle of 5°.

The maximum reflectance of light having wavelengths in the range of 430to 700 nm is preferably 1.5% or smaller and more preferably 1.4% orsmaller at an incident angle of 20°, and the reflectance of light havinga wavelength of 550 nm is preferably 0.9% or smaller and more preferably0.8% or smaller at an incident angle of 20°.

When each reflectance is within the respective range described above, apolarizer plate showing no images from outside light or glare andproviding excellent vision can be obtained.

As for the reflectances described above, the reflectance of light havinga wavelength of 550 nm and the maximum reflectance of light havingwavelengths in the range of 430 to 700 nm are obtained at incidentangles of 5° and 20° using a spectrophotometer (an ultraviolet, visibleand near infrared spectrophotometer V-550; manufactured by NIPPON BUNKOCo., Ltd.).

The steel wool test is conducted by reciprocally moving steel wool #0000ten times on the surface of a protective film of a polarizer at the sideof vision under application of a load of 0.025 MPa, and then the changein the condition of the surface after the test is measured.

For evaluation of the change in the reflectance before and after thesteel wool test, the measurement is conducted at arbitrarily selected 5different positions on the surface before and after the test, and thearithmetic average of the obtained values is calculated.

In the above steel wool test, the change in the reflectance on theprotective film of a polarizer at the side of vision before and afterthe test is preferably 10% or smaller and more preferably 8% or smaller.When the change in the reflectance exceeds 10%, blurred images may beformed or glare may arise.

The change in the reflectance before and after the steel wool test isobtained in accordance with the following equation (1.1). R^(b)represents the reflectance before the steel wool test, and R^(a)represents the reflectance after the steel wool test.ΔR=(R ^(b) −R ^(a))/R ^(b)×100(%)  (1.1)

The embodiments of the liquid crystal display device of the presentinvention comprising optically anisotropic member (A) and opticallyanisotropic member (B) comprise 12 embodiments of the preferablearrangement. In the following, 6 embodiments of the preferablearrangement in which “the polarizer of the output side” is placed at theside of vision, and “the polarizer of the incident side” is placed atthe side of the back light will be described. The remaining 6embodiments of the preferable arrangement are embodiments of thepreferable arrangement obtained by exchanging the polarizer at the sideof vision and the polarizer at the side of the back light with eachother (i.e., the arrangement in which “the polarizer of the incidentside” is placed at the side of vision, and “the polarizer of the outputside” is placed at the side of the back light). These embodiments of thepreferable arrangement show the same characteristics of the angle offield with those before the exchange of the polarizer at the side ofvision and the polarizer at the side of the back light with each other.For example, the embodiments of the preferable arrangement shown in FIG.1 and FIG. 2 show the same characteristics of the angle of field withrespect to luminance, contrast and color tone. The arrow in the figuresshows the absorption axis for the polarizers (1: the polarizer at theincident side; 5: the polarizer at the output side), the in-plane slowaxis under application of no voltage for the liquid crystal cell 2, andthe in-plane slow axis for the optically anisotropic members (3:optically anisotropic member (A); 4: optically anisotropic member (B).

In the first and second embodiments of the preferable arrangement,optically anisotropic member (A) and optically anisotropic member (B)are disposed between the polarizer at the incident side (the polarizerat the side of the back light) and the liquid crystal cell of the liquidcrystal display device.

(I-1) The First Embodiment of the Preferable Arrangement

FIG. 3 shows a diagram exhibiting the first embodiment of the preferablearrangement (referred to as arrangement I-1, hereinafter) of the liquidcrystal display device of the present invention. In arrangement I-1, theabsorption axis of the polarizer at the output side and the in-planeslow axis of the liquid crystal of the liquid crystal cell underapplication of no voltage are disposed at relative positions parallel toeach other. The in-plane slow axes of optically anisotropic member (A)and optically anisotropic member (B) are disposed at relative positionsapproximately parallel to each other. It is preferable that the in-planeslow axis of optically anisotropic member (B) and the in-plane slow axisof the liquid crystal of the liquid crystal cell under application of novoltage are disposed at relative positions approximately parallel toeach other, and optically anisotropic member (A) is disposed at aposition closer to the liquid cell than optically anisotropic member(B). Due to the above relative positions of optically anisotropic member(A), optically anisotropic member (B), the liquid crystal cell and thetwo polarizers, the minimum value of the contrast can be made 30 orgreater at polar angles of 0 to 80°.

In arrangement I-1, the preferable combination of the in-planeretardation R_(e)(A) (the unit: nm) and the retardation in the directionof the thickness R_(th)(A) (the unit: nm) of optically anisotropicmember (A) and the in-plane retardation R_(e)(B) (the unit: nm) and theretardation in the direction of the thickness R_(th)(B) (the unit: nm)of optically anisotropic member (B) is: 10≦R_(e)(A)≦1,000,−500≦R_(th)(A)≦−5, 10≦R_(e)(B)≦500 and 5≦R_(th)(B)≦250. The morepreferable combinations are: (1) 10≦R_(e)(A)≦360, −180≦R_(th)(A)≦−5,10≦R_(e)(B)≦360 and 5≦R_(th)(B)≦360; (2) 350≦R_(e)(A)≦470,−235≦R_(th)(A)≦−175, 450≦R_(e)(B)≦500 and 225 R_(th)(B)≦250; and (3)640≦R_(e)(A)≦700, −350≦R_(th)(A)≦−320, 20≦R_(e)(B)≦100 and10≦R_(th)(B)≦50. The still more preferable combination is:30≦R_(e)(A)≦320, −160≦R_(th)(A)≦−15, 30≦R_(e)(B)≦320 and20≦R_(th)(B)≦−320. The most preferable combination is: 70≦R_(e)(A)≦120,−65≦R_(th)(A)≦−25, 50≦R_(e)(B)≦110 and 25≦R_(th)(B)≦70.

In the present invention, the in-plane retardation R_(e) and theretardation in the direction of thickness R_(th) can be obtained inaccordance with the following equations (1.2) and (1.3). In theequations, n_(x), n_(y) and n_(z) each represent the refractive index(−), and d represents the thickness (nm).R _(e)=(n _(x) −n _(y))×d  (1.2)R _(th)=[(n _(x) +n _(y))/2−n _(z) ]×d  (1.3)(I-2) The Second Embodiment of the Preferable Arrangement

FIG. 4 shows a diagram exhibiting the second embodiment of thepreferable arrangement (referred to as arrangement I-2, hereinafter) ofthe liquid crystal display device of the present invention. Inarrangement I-2, the absorption axis of the polarizer at the output sideand the in-plane slow axis of the liquid crystal of the liquid crystalcell under application of no voltage are disposed at relative positionsparallel to each other. The in-plane slow axes of optically anisotropicmember (A) and optically anisotropic member (B) are disposed at relativepositions approximately parallel to each other. It is preferable thatthe in-plane slow axis of optically anisotropic member (B) and thein-plane slow axis of the liquid crystal of the liquid crystal cellunder application of no voltage are disposed at relative positionsapproximately perpendicular to each other, and optically anisotropicmember (B) is disposed at a position closer to the liquid cell thanoptically anisotropic member (A). Due to the above relative positions ofoptically anisotropic member (A), optically anisotropic member (B), theliquid crystal cell and the two polarizers, the minimum value of thecontrast can be made 30 or greater at polar angles of 0 to 80°.

In arrangement I-2, the preferable combination of the in-planeretardation R_(e)(A) (the unit: nm) and the retardation in the directionof the thickness R_(th)(A) (the unit: nm) of optically anisotropicmember (A) and the in-plane retardation R_(e)(B) (the unit: nm) and theretardation in the direction of the thickness R_(th)(B) (the unit: nm)of optically anisotropic member (B) is: 10≦R_(e)(A)≦1,000,−500≦R_(th)(A)≦−5, 10≦R_(e)(B)≦1,000 and 5≦R_(th)(B)≦500. The morepreferable combinations are: (1) 10≦R_(e)(A)≦310, −240 R_(th)(A)≦−5,10≦R_(e)(B)≦300 and 5≦R_(th)(B)≦100; (2) 350≦R_(e)(A)≦470,−235≦R_(th)(A)≦−175, 450≦R_(e)(B)≦500 and 225≦R_(th)(B)≦250; (3)640≦R_(e)(A)≦700, −350≦R_(th)(A)≦−320, 20≦R_(e)(B)≦100 and10≦R_(th)(B)≦50; and (4) 730≦R_(e)(A)≦760, −570≦R_(th)(A)≦−540,240≦R_(e)(B)≦280 and 120≦R_(th)(B)≦140. The still more preferablecombination is: 30≦R_(e)(A)≦150, −90≦R_(th)(A)≦−15, 40≦R_(e)(B)≦150 and20≦R_(th)(B)≦75. The most preferable combination is: 60≦R_(e)(A)≦110,−70≦R_(th)(A)≦−25, 70≦R_(e)(B)≦120 and 25≦R_(th)(B)≦65.

In the third and fourth embodiments of the preferable arrangement,optically anisotropic member (A) and optically anisotropic member (B)are disposed between the polarizer at the output side (the polarizer atthe side of vision) and the liquid crystal cell of the liquid crystaldisplay device.

(II-1) The Third Embodiment of the Preferable Arrangement

FIG. 5 shows a diagram exhibiting the third embodiment of the preferablearrangement (referred to as arrangement II-1, hereinafter) of the liquidcrystal display device of the present invention. In arrangement II-1,the absorption axis of the polarizer at the output side and the in-planeslow axis of the liquid crystal of the liquid crystal cell underapplication of no voltage are disposed at relative positions parallel toeach other. The in-plane slow axes of optically anisotropic member (A)and optically anisotropic member (B) are disposed at relative positionsapproximately parallel to each other. It is preferable that the in-planeslow axis of optically anisotropic member (B) and the in-plane slow axisof the liquid crystal of the liquid crystal cell under application of novoltage are disposed at relative positions approximately perpendicularto each other, and optically anisotropic member (A) is disposed at aposition closer to the liquid cell than optically anisotropic member(B). Due to the above relative positions of optically anisotropic member(A), optically anisotropic member (B), the liquid crystal cell and thetwo polarizers, the minimum value of the contrast can be made 30 orgreater at polar angles of 0 to 80°.

In arrangement II-1, the preferable combination of the in-planeretardation R_(e)(A) (the unit: nm) and the retardation in the directionof the thickness R_(th)(A) (the unit: nm) of optically anisotropicmember (A) and the in-plane retardation R_(e)(B) (the unit: nm) and theretardation in the direction of the thickness R_(th)(B) (the unit: nm)of optically anisotropic member (B) is: 10≦R_(e)(A)≦1,000,−500≦R_(th)(A)≦−5, 10≦R_(e)(B)≦1,000 and 5≦R_(th)(B)≦500. The morepreferable combinations are: (1) 150≦R_(e)(A)≦470, −235≦R_(th)(A)≦−75,20≦R_(e)(B)≦480 and 10≦R_(th)(B)≦240; and (2) 640≦R_(e)(A)≦760,−380≦R_(th)(A)≦−320, 370≦R_(e)(B)≦470 and 185≦R_(th)(B)≦235. The stillmore preferable combination is: 320≦R_(e)(A)≦400, −200≦R_(th)(A)≦−160,50≦R_(e)(B)≦170 and 25≦R_(th)(B)≦85. The most preferable combination is:340≦R_(e)(A)≦380, −200≦R_(th)(A)≦−160, 90≦R_(e)(B)≦130 and35≦R_(th)(B)≦75.

(II-2) The Fourth Embodiment of the Preferable Arrangement

FIG. 6 shows a diagram exhibiting the fourth embodiment of thepreferable arrangement (referred to as arrangement II-2, hereinafter) ofthe liquid crystal display device of the present invention. Inarrangement II-2, the absorption axis of the polarizer at the outputside and the in-plane slow axis of the liquid crystal of the liquidcrystal cell under application of no voltage are disposed at relativepositions parallel to each other, and the absorption axis of thepolarizer at the output side and the in-plane slow axis of the liquidcrystal of the liquid crystal cell under application of no voltage aredisposed at relative positions parallel to each other. The in-plane slowaxes of optically anisotropic member (A) and optically anisotropicmember (B) are disposed at relative positions approximately parallel toeach other. It is preferable that the in-plane slow axis of opticallyanisotropic member (B) and the in-plane slow axis of the liquid crystalof the liquid crystal cell under application of no voltage are disposedat relative positions approximately parallel to each other, andoptically anisotropic member (B) is disposed at a position closer to theliquid cell than optically anisotropic member (A). Due to the aboverelative positions of optically anisotropic member (A), opticallyanisotropic member (B), the liquid crystal cell and the two polarizers,the minimum value of the contrast can be made 20 or greater at polarangles of 0 to 80°.

In arrangement II-2, the preferable combination of the in-planeretardation R_(e)(A) (the unit: nm) and the retardation in the directionof the thickness R_(th)(A) (the unit: nm) of optically anisotropicmember (A) and the in-plane retardation R_(e)(B) (the unit: nm) and theretardation in the direction of the thickness R_(th)(B) (the unit: nm)of optically anisotropic member (B) is: 10≦R_(e)(A)≦−1,000,−500≦R_(th)(A)≦−5, 100≦R_(e)(B)≦450 and 50≦R_(th)(B)≦225. The mostpreferable combination is: 420≦R_(e)(A)≦460, −240≦R_(th)(A)≦−200,170≦R_(e)(B)≦210 and 75≦R_(th)(B)≦115.

In the fifth and sixth embodiments of the preferable arrangement, one ofoptically anisotropic member (A) and optically anisotropic member (B) isdisposed between the polarizer at the incident side and the liquidcrystal cell and the other is disposed between the polarizer at theoutput side and the liquid crystal cell.

(III-1) The Fifth Embodiment of the Preferable Arrangement

FIG. 7 shows a diagram exhibiting the fifth embodiment of the preferablearrangement (referred to as arrangement III-1, hereinafter) of theliquid crystal display device of the present invention. In arrangementIII-1, the absorption axis of the polarizer at the output side and thein-plane slow axis of the liquid crystal of the liquid crystal cellunder application of no voltage are disposed at relative positionsparallel to each other. The in-plane slow axes of optically anisotropicmember (A) and optically anisotropic member (B) are disposed at relativepositions approximately parallel to each other. It is preferable thatthe in-plane slow axis of optically anisotropic member (A) and thein-plane slow axis of the liquid crystal of the liquid crystal cellunder application of no voltage are disposed at relative positionsapproximately perpendicular to each other, optically anisotropic member(A) is disposed between the liquid crystal cell and the polarizer at theincident side, and optically anisotropic member (B) is disposed betweenthe liquid crystal cell and the polarizer at the output side. Due to theabove relative positions of optically anisotropic member (A), opticallyanisotropic member (B), the liquid crystal cell and the two polarizers,the minimum value of the contrast can be made 30 or greater at polarangles of 0 to 80°.

In arrangement III-1, the preferable combination of the in-planeretardation R_(e)(A) (the unit: nm) and the retardation in the directionof the thickness R_(th)(A) (the unit: nm) of optically anisotropicmember (A) and the in-plane retardation R_(e)(B) (the unit: nm) and theretardation in the direction of the thickness R_(th)(B) (the unit: nm)of optically anisotropic member (B) is: 10≦R_(e)(A)≦720,−360≦R_(th)(A)≦−5, 10≦R_(e)(B)≦1,000 and −500≦R_(th)(B)≦−5. The morepreferable combinations are: (1) 170≦R_(e)(A)≦230, −115≦R_(th)(A)≦−85,400≦R_(e)(B)≦460 and 200≦R_(th)(B)≦230; and (2) 270≦R_(e)(A)≦440,−220≦R_(th)(A)≦−135, 20≦R(B)≦190 and 10≦R_(th)(B)≦95. The still morepreferable combination is: 310≦R_(e)(B)≦410, −205≦R_(th)(A)≦−155,50≦R_(e)(B)≦140 and 25≦R_(th)(B)≦70. The most preferable combination is:340≦R_(e)(A)≦380, −200≦R_(th)(B)≦−160, 70≦R_(e)(B)≦110 and25≦R_(th)(B)≦65.

(III-2) The Sixth Embodiment of the Preferable Arrangement

FIG. 8 shows a diagram exhibiting the sixth embodiment of the preferablearrangement (referred to as arrangement III-2, hereinafter) of theliquid crystal display device of the present invention. In arrangementIII-2, the absorption axis of the polarizer at the output side and thein-plane slow axis of the liquid crystal of the liquid crystal cellunder application of no voltage are disposed at relative positionsparallel to each other. The in-plane slow axes of optically anisotropicmember (A) and optically anisotropic member (B) are disposed at relativepositions approximately parallel to each other. It is preferable thatthe in-plane slow axis of optically anisotropic member (A) and thein-plane slow axis of the liquid crystal of the liquid crystal cellunder application of no voltage are disposed at relative positionsapproximately parallel to each other, optically anisotropic member (B)is disposed between the liquid crystal cell and the polarizer at theincident side, and optically anisotropic member (A) is disposed betweenthe liquid crystal cell and the polarizer at the output side. Due to theabove relative positions of optically anisotropic member (A), opticallyanisotropic member (B), the liquid crystal cell and the two polarizers,the minimum value of the contrast can be made 20 or greater at polarangles of 0 to 80°.

In arrangement III-1, the preferable combination of the in-planeretardation R_(e)(A) (the unit: nm) and the retardation in the directionof the thickness R_(th)(A) (the unit: nm) of optically anisotropicmember (A) and the in-plane retardation R_(e)(B) (the unit: nm) and theretardation in the direction of the thickness R_(th)(B) (the unit: nm)of optically anisotropic member (B) is: 10≦R_(e)(A)≦1,000,−500≦R_(th)(A)≦−5, 120≦R_(e)(B)≦440 and 60≦R_(th)(B)≦220. The mostpreferable combination is: 40≦R_(e)(A)≦80, −50≦R_(th)(A)≦−10,340≦R_(e)(B)≦380 and 160≦R_(th)(B)≦200.

In the liquid crystal display device of the present invention, suitablemembers such as prism array sheets, lens array sheets, light diffusionplates, back lights and films for increasing luminance may be disposedat suitable positions as one or more layers.

In the liquid crystal display device of the present invention, a coldcathode tube, a horizontal mercury lamp, a light emitting diode or anelectroluminescence device may be used as the back light.

EXAMPLES

The present invention will be described more specifically with referenceto examples in the following. However, the present invention is notlimited to the examples.

In Examples and Comparative Example, a polarizer plate which was alaminate of a polarizer and a protective film for the polarizer[manufactured by SANRITZ Co., Ltd.; HLC 2-5618] was used. As the liquidcrystal cell, a liquid crystal cell of the in-plane switching modehaving a thickness of 2.74 μm, a positive dielectric anisotropy, abirefringence of Δn=0.09884 at a wavelength of 550 nm and a pretiltangle of 0° was used.

In Examples and Comparative Example, measurements and evaluations wereconducted in accordance with the following methods.

(1) Thickness

After a laminate for optical applications was embedded into an epoxyresin, the laminate was sliced into pieces having a thickness of 0.05 μmusing a microtome [manufactured by YAMATO KOKI KOGYO Co., Ltd.;RUB-2100], and the thickness of each piece was measured by observing thesection using a transmission electron microscope.

(2) Glass Transition Temperature

The glass transition temperature was measured in accordance with themethod of differential scanning calorimetry (DSC) described in JapaneseIndustrial Standard K 7121.

(3) Refractive Indices (n_(x), n_(y) and n_(z)), Retardations (in-PlaneRetardation R_(e) and Retardation in the Direction of Thickness R_(th))and Dispersion of the in-Plane Retardations of Optically AnisotropicMember (A) and Optically Anisotropic Member (B)

For the measurement of the refractive indices of optically anisotropicmember (A) and optically anisotropic member (B), the direction of thein-plane slow axis of the anisotropic member with respect to lighthaving a wavelength of 550 nm was measured using an automaticbirefringence meter [manufactured by OJI KEISOKUKIKI Co., Ltd.;KOBRA-21]. Then, the refractive index of the anisotropic member in thedirection of the slow axis was measured as n_(x), the refractive indexin the direction in-plane and perpendicular to the direction of the slowaxis was measured as n_(y), and the refractive index in the direction ofthe thickness of the anisotropic member was measured as n_(z). When theoptically anisotropic member was a laminate, n_(x), n_(y) and n_(z) werecalculated in accordance with the following equations after therefractive indices (n_(xi), n_(yi) and n_(zi)) of each layer had beenmeasured. In each layer of the laminate, the refractive index in thedirection parallel to the slow axis of the optically anisotropicsubstance is represented by n_(xi), the refractive index in thedirection in-plane and perpendicular to the slow axis is represented byn_(yi), and the refractive index in the direction of the thickness isrepresented by n_(zi).n _(x)=[Σ(n _(xi) ×d _(i))]/[(Σd _(i)); n _(y)=[Σ(n _(yi) ×d _(i))]/[(Σd_(i)); n _(z)=[Σ(n _(zi1) ×d _(i))]/[(Σd _(i))wherein Σ means the total sum, each layer in the anisotropic member isindicated by i (i=1, 2 . . . ), and the thickness of each layer isrepresented by d_(i1), d_(i2) . . . .

The retardations R_(e) and R_(th) were measured with respect to lighthaving a wavelength of 550 nm using the above automatic birefringencemeter.

As for the dispersion of the in-plane retardation, the in-planeretardation was measured at 30 positions arbitrarily selected over theentire surface of the anisotropic member, and the arithmetic average ofthe obtained values was used as the value of the in-plane retardation.The difference between the maximum value and the minimum value among thevalues obtained by the measurement was used as the dispersion of thein-plane retardation.

(4) Content of Residual Volatile Components

An optically anisotropic member in an amount of 200 g was placed into atube having an inner diameter of 4 mm used as the container of thesample, which had been treated in advance to completely remove moistureand organic substances adsorbed on the surface. Then, the container washeated at a temperature of 100° C. for 60 minutes, and the gasdischarged from the container was continuously trapped. The trapped gaswas analyzed by a thermal desorption gas chromatography mass analyzer(TDS-GC-MS), and the total of the contents of components having amolecular weight of 200 or smaller among the components of the gas wasobtained and used as the content of residual volatile components.

(5) Refractive Indices of a Hard Coat Layer and a Low Refractive IndexLayer

The measurement was conducted at a wavelength of 245 to 1,000 nm andincident angles of 55°, 60° and 65° using a high speed spectroscopicelipsometer [manufactured by J. A. WOOLAM Company; M-2000U], and therefractive indices were obtained by calculation based on the valuesobtained by the measurement.

(6) Reflectance

The reflection spectrum was measured at an incident angle of 5° using aspectrophotometer [manufactured by NIPPON BUNKO Co., Ltd.; “Ultraviolet,visible and near-infrared spectrophotometer V-570”], and the reflectanceat a wavelength of 550 nm and the maximum value of the reflectance atwavelengths in the range of 430 to 700 nm were obtained.

(7) Angle of Field of a Liquid Crystal Display Device

Optically anisotropic member (A) and optically anisotropic member (B)were disposed in a liquid crystal display device of the in-planeswitching (IPS) mode, and the display characteristic was examined byvisual observation directly in front of the display and in obliquedirections at polar angles of 800 and smaller.

(8) Nonuniformity of Luminance

Optically anisotropic member (A) and optically anisotropic member (B)were disposed in a liquid crystal display device of the in-planeswitching (IPS) mode. The background of the display was adjusted to thedark display, and the presence or the absence of nonuniformity ofluminance (white spots) was examined by visual observation in a darkroom directly in front of the display and in upward, downward, rightwardand leftward oblique directions each at a polar angle of 40°.

(9) Scratch Resistance

Steel wool #0000 was pressed to a polarizer plate at the side havinglaminated layers of a hard coat layer and a low refractive index layer.After the steel wool was moved reciprocally 10 times under a load of0.05 MPa, the condition of the surface of the polarizer plate after the10 reciprocal movements was visually observed.

Preparation Example 1 Preparation of a Film of Optically AnisotropicMember (A1)

An unstretched laminate which comprised layer [1] comprising anorbornene-based polymer [manufacture by NIPPON ZEON Co., Ltd.; ZEONOR1020; the glass transition temperature: 105° C.], layer [2] comprising astyrene-maleic anhydride copolymer [the glass transition temperature:130° C.; the content of oligomer components: 3% by weight] and layer [3]comprising a modified ethylene-vinyl acetate copolymer [the Vicatsoftening point: 80° C.] and had a structure of layer [1] (8 μm)—layer[3] (2 μm)—layer [2] (16 μm)—layer [3] (2 μm)—layer [1] (8 μm) wasobtained in accordance with the coextrusion molding. The unstretchedlaminate was uniaxially stretched in the longitudinal direction by a niproll at a temperature of 134° C. at a stretching speed of 114%/min to astretching ratio of 1.4, and a long sheet of a film having the slow axisin the transverse direction of the film, optically anisotropic member(A1), was obtained.

Optically anisotropic member (A1) had refractive indices of n_(xA):1.57130, n_(yA):1.57012, n_(zA):1.57130, an in-plane retardation R_(e)of 110 nm, a retardation in the direction of the thickness R_(th) of −55nm, and a content of residual volatile components of 0.01% or smaller.

Preparation Example 2 Preparation of a Film of Optically AnisotropicMember (B1)

Unstretched single layer film (b1) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420; the glass transitiontemperature: 136° C.] was obtained in accordance with the extrusionmolding. Unstretched single layer film (b1) was uniaxially stretched inthe transverse direction by a tenter at a temperature of 140° C. at astretching speed of 92%/min to a stretching ratio of 1.3, and a longsheet of a film having the slow axis in the transverse direction of thefilm, optically anisotropic member (B1), was obtained.

Optically anisotropic member (B1) had refractive indices ofn_(xB):1.53109, n_(yB):1.53011, n_(zB):1.52962, an in-plane retardationR_(e) of 60 nm, a retardation in the direction of the thickness R_(th)of 60 nm, and a content of residual volatile components of 0.01% orsmaller.

Preparation Example I Preparation of a Hard Coating Agent

To 100 parts by weight of a modified alcohol sol of antimony pentaoxide[the concentration of solid components: 30% by weight; manufactured bySHOKUBAI KASEI Co., Ltd.], 10 parts by weight of a urethane acrylate ofthe ultraviolet light curing type [the trade name: SHIKO UV7000B;manufactured by NIPPON GOSEI KAGAKU Co., Ltd.] and 0.4 parts by weightof a photopolymerization initiator [the trade name: IRGACURE 184;manufactured by CIBA GEIGY Company] were mixed, and a hard coating agentof the ultraviolet light curing type was obtained.

Preparation Example II Preparation of a Coating Fluid for a LowRefractive Index Layer

To 208 parts by weight of tetraethoxysilane, 356 parts by weight ofmethanol was added. Then, 18 parts by weight of water and 18 parts byweight of 0.01N hydrochloric acid were mixed with the resultantsolution, and the obtained mixture was mixed well by a disper. The mixedsolution was stirred for 2 hours in a vessel kept at 25° C., and atetrafunctional silicone resin having a weight-average molecular weightof 850 was obtained. To the tetrafunctional silicone resin, a dispersionsol of hollow silica in isopropanol (IPA) [the content of solidcomponents: 20% by mass; the average diameter of primary particles: 35nm: the thickness of the outer shell: about 8 nm; manufactured bySHOKUBAI KASEI KOGYO Co., Ltd.] as the component of fine particles ofhollow silica was added in an amount such that the ratio of the amountsby mass of solid components in the hollow silica fine particles to thosein the tetrafunctional silicone resin (calculated as condensedcompounds) was 85/25. The resultant mixture was diluted with methanol sothat the content of the entire solid components was 10% by mass, and acoating fluid for a low refractive index layer was obtained.

Preparation Example III Preparation of a Hard Coat Layer

One face of a long sheet of a polarizer plate [manufactured by SANRITZCompany; HLC2-5618S] was treated by corona discharge for 3 seconds usinga high frequency oscillator [CORONA GENERATOR HV05-2; manufactured byTAMTEC Company], and the surface was modified so that the surfacetension was 0.072 N/m. The surface modified above was continuouslycoated with the hard coating agent obtained in Preparation Example Iusing a die coater in a manner such that the thickness of the hard coatlayer obtained after being cured was 5 μm. After the coating layer wasdried at 80° C. for 5 minutes, the coating layer was irradiated withultraviolet light (the accumulated amount of light: 300 mJ/cm²) to curethe hard coating agent, and a long sheet of polarizer plate (C′)laminated with the hard coat layer was obtained. The hard coat layer hada thickness of 5 μm, a refractive index of 1.62 and a surface roughnessof 0.2 μm after being cured.

Preparation Example IV Preparation of a Low Refractive Index Layer

The long sheet of polarizer plate (C′) laminated with the hard coatlayer was coated with the coating fluid for a low refractive index layerobtained in Preparation Example II as the material constituting the lowrefractive index layer using a wire bar coater. After the heat treatmentin the air at 120° C. for 5 minutes, a long sheet of polarizer plate (C)laminated with the low refractive index layer and the hard coat layer inwhich the low refractive index layer had a thickness of 100 nm wasobtained. The refractive index of the obtained low refractive indexlayer was 1.34.

Example 1 Preparation of a Liquid Crystal Display Device LCD-1

Optical element (b′1) was obtained by laminating the long sheet ofoptically anisotropic member (B1) obtained in Preparation Example 2 anda long sheet of a polarizer plate (manufactured by SANRITZ Company;HLC2-5618) in accordance with the roll-to-roll process. The anglebetween the slow axis of optically anisotropic member (B1) and theabsorption axis of the polarizer plate was 900.

Optical element (a′1) was obtained by laminating the long sheet ofoptically anisotropic member (A1) obtained in Preparation Example 1 andoptical element (b′1) obtained above in accordance with the roll-to-rollprocess. The angle between the slow axis of optically anisotropic member(A1) and the absorption axis of optical element (b′1) obtained above was90°. A plate obtained by cutting out of optical element (a′1) obtainedabove was used as polarizer plate of the incident side (A′1).

A polarizer plate at the incident side in a commercial liquid crystaldisplay device of the in-plane switching (IPS) mode was replaced withpolarizer plate of the incident side (A′1). The polarizer plate at theoutput side in the liquid crystal display device was replaced with aplate obtained by cutting out of the long sheet of polarizer plate (C)laminated with the low refractive index layer and the hard coat layerwhich was obtained Preparation Example IV. The members of the liquidcrystal display device were arranged in a manner such that theabsorption axis of polarizer plate of the output side and the in-planeslow axis of the liquid crystal cell under application of no voltagewere parallel to each other, and the absorption axis of polarizer plateof the incident side (A′1) and the in-plane slow axis of the liquidcrystal cell under application of no voltage were perpendicular to eachother, and a liquid crystal display device having the structure shown inFIG. 3, LCD-1, was prepared. The obtained device had a structure inwhich the members were disposed in the following order from the side ofvision of the liquid crystal display device: the low refractive indexlayer, the hard coat layer, the polarizer plate, the liquid crystalcell, the film of optically anisotropic member (A1) obtained inPreparation Example 1, the film of optically anisotropic member (B1)obtained in Preparation Example 2, and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-1 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Preparation Example 3 Preparation of a Film of Optically AnisotropicMember (A2)

An unstretched laminate which comprised layer [1] comprising anorbornene-based polymer [manufacture by NIPPON ZEON Co., Ltd.; ZEONOR1020; the glass transition temperature: 105° C.], layer [2] comprising astyrene-maleic anhydride copolymer [the glass transition temperature:130° C.; the content of oligomer components: 3% by weight] and layer [3]comprising a modified ethylene-vinyl acetate copolymer [the Vicatsoftening point: 80° C.] and had a structure of layer [1] (8 μm)—layer[3] (2 μm)—layer [2] (16 μm)—layer [3] (2 μm)—layer [1] (8 μm) wasobtained in accordance with the coextrusion molding. The unstretchedlaminate was uniaxially stretched in the transverse direction by atenter at a temperature of 132° C. at a stretching speed of 104%/min toa stretching ratio of 1.35, and a long sheet of a film having the slowaxis in the longitudinal direction of the film, optically anisotropicmember (A2), was obtained.

Optically anisotropic member (A2) had refractive indices ofn_(xA):1.53129, n_(yA):1.53011, n_(zA):1.53160, an in-plane retardationR_(e) of 70 nm, a retardation in the direction of the thickness R_(th)of −52.5 nm, and a content of residual volatile components of 0.01% orsmaller.

Preparation Example 4 Preparation of a Film of Optically AnisotropicMember (B2)

Unstretched single layer film (b2) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420; the glass transitiontemperature: 136° C.] was obtained in accordance with the extrusionmolding. Unstretched single layer film (b2) was uniaxially stretched inthe longitudinal direction by a nip roll at a temperature of 134° C. ata stretching speed of 104%/min to a stretching ratio of 1.35, and a longsheet of a film having the slow axis in the longitudinal direction ofthe film, optically anisotropic member (B2), was obtained.

Optically anisotropic member (B2) had refractive indices of n_(xB):1.53156, n_(yB):1.53011, n_(zB):1.53011, an in-plane retardation R_(e)of 100 nm, a retardation in the direction of the thickness R_(th) of 50nm, and a content of residual volatile components of 0.01% or smaller.

Example 2 Preparation of a Liquid Crystal Display Device LCD-2

Optical element (a′2) was obtained by laminating the long sheet ofoptically anisotropic member (A2) obtained in Preparation Example 3 anda long sheet of a polarizer plate (manufactured by SANRITZ Company;HLC2-5618) in accordance with the roll-to-roll process. The anglebetween the slow axis of optically anisotropic member (A2) and theabsorption axis of the polarizer plate was 0°.

Optical element (b′2) was obtained by laminating the long sheet ofoptically anisotropic member (B2) obtained in Preparation Example 4 andoptical element (a′2) obtained above in accordance with the roll-to-rollprocess. The angle between the slow axis of optically anisotropic member(B2) and the absorption axis of optical element (a′2) obtained above was0°. A plate obtained by cutting out of optical element (b′2) obtainedabove was used as polarizer plate of the incident side (B′1).

A polarizer plate at the incident side in a commercial liquid crystaldisplay device of the in-plane switching (IPS) mode was replaced withpolarizer plate of the incident side (B′1). The polarizer plate at theoutput side in the liquid crystal display device was replaced with aplate obtained by cutting out of the long sheet of polarizer plate (C)laminated with the low refractive index layer and the hard coat layerwhich was obtained Preparation Example IV. The members of the liquidcrystal display device were arranged in a manner such that theabsorption axis of polarizer plate of the output side and the in-planeslow axis of the liquid crystal cell under application of no voltagewere parallel to each other, and the absorption axis of polarizer plateof the incident side (A′2) and the in-plane slow axis of the liquidcrystal cell under application of no voltage were perpendicular to eachother, and a liquid crystal display device having the structure shown inFIG. 4, LCD-2, was prepared. The obtained device had a structure inwhich the members were disposed in the following order from the side ofvision of the liquid crystal display device: the low refractive indexlayer, the hard coat layer, the polarizer plate, the liquid crystalcell, the film of optically anisotropic member (B2) obtained inPreparation Example 4, the film of optically anisotropic member (A2)obtained in Preparation Example 3, and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-2 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Preparation Example 5 Preparation of a Film of Optically AnisotropicMember (A3)

A long sheet of unstretched film (a3) comprising a norbornene-basedpolymer [manufactured by NIPPON ZEON Co., Ltd.; ZEONOR 1420R; the glasstransition temperature: 136° C.] and having a thickness of 100 μm wasobtained in accordance with the extrusion molding. Unstretched film (a3)obtained above had a content of residual volatile components of 0.01% orsmaller.

The above unstretched film (a3) was coated with a solution containing 8%by weight of the lyotropic liquid crystal expressed by formula (3) shownabove and 92% by weight of water using a die coater under shearing forcein the direction parallel to the transverse direction of the filmwithout using a film for orientation. The coated film was left standingunder an atmosphere heated at 118° C. (after being purged with argon) toremove water, and a film of optically anisotropic member (A3) wasobtained. The lyotropic liquid crystal molecules were arranged in thehomogeneous orientation in a manner such that the slow axis was orientedin the longitudinal direction of the transparent polymer film.

Optically anisotropic member (A3) obtained above had refractive indicesof n_(xA):1.63387, n_(yA):1.54203 and n_(xA):1.63387, an in-planeretardation R_(e) of 90 nm, and a retardation in the direction of thethickness R_(th) of −45 nm.

Preparation Example 6 Preparation of a Film of Optically AnisotropicMember (B3)

Unstretched single layer film (b3) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420; the glass transitiontemperature: 136° C.] was obtained in accordance with the extrusionmolding. Unstretched single layer film (b3) was uniaxially stretched inthe longitudinal direction by a nip roll at a temperature of 133° C. ata stretching speed of 92%/min to a stretching ratio of 1.3, and a longsheet of a film having the slow axis in the longitudinal direction ofthe film, optically anisotropic member (B3), was obtained.

Optically anisotropic member (B3) had refractive indices of n_(xB):1.53125, n_(yB):1.53011, n_(zB):1.53011, an in-plane retardation R_(e)of 90 nm, a retardation in the direction of the thickness R_(th) of 45nm, and a content of residual volatile components of 0.01% or smaller.

Example 3 Preparation of a Liquid Crystal Display Device LCD-3

Optical element (a′3) was obtained by laminating the long sheet ofoptically anisotropic member (A3) obtained in Preparation Example 5 anda long sheet of a polarizer plate (manufactured by SANRITZ Company;HLC2-5618) in accordance with the roll-to-roll process in a manner suchthat the side of the layer of the lyotropic liquid crystal in opticallyanisotropic member (A3) was placed towards the polarizing plate. Theangle between the slow axis of optically anisotropic member (A3) and theabsorption axis of the polarizer plate was 0°.

Optical element (b′3) was obtained by laminating the long sheet ofoptically anisotropic member (B3) obtained in Preparation Example 6 andoptical element (a′3) obtained above in accordance with the roll-to-rollprocess. The angle between the slow axis of optically anisotropic member(B3) and the absorption axis of optical element (a′3) obtained above was0°. A plate obtained by cutting out of optical element (b′3) obtainedabove was used as polarizer plate of the incident side (B′3).

A polarizer plate at the incident side in a commercial liquid crystaldisplay device of the in-plane switching (IPS) mode was replaced withpolarizer plate of the incident side (B′3). The polarizer plate at theoutput side in the liquid crystal display device was replaced with aplate obtained by cutting out of the long sheet of polarizer plate (C)laminated with the low refractive index layer and the hard coat layerwhich was obtained Preparation Example IV. The members of the liquidcrystal display device were arranged in a manner such that theabsorption axis of the polarizer plate of the output side and thein-plane slow axis of the liquid crystal cell under application of novoltage were parallel to each other, and the absorption axis ofpolarizer plate of the incident side (B′3) and the in-plane slow axis ofthe liquid crystal cell under application of no voltage wereperpendicular to each other, and a liquid crystal display device havingthe structure shown in FIG. 4, LCD-3, was prepared. The obtained devicehad a structure in which the members were disposed in the followingorder from the side of vision of the liquid crystal display device: thelow refractive index layer, the hard coat layer, the polarizer plate,the liquid crystal cell, the film of optically anisotropic member (B3)obtained in Preparation Example 6, the film of optically anisotropicmember (A3) obtained in Preparation Example 5, and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-3 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Preparation Example 7 Preparation of a Film of Optically AnisotropicMember (A4)

A long sheet of unstretched film (a4) comprising a norbornene-basedpolymer [manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420R; the glasstransition temperature: 136° C.] and having a thickness of 100 μm wasobtained in accordance with the extrusion molding. Unstretched film (a4)obtained above had a content of residual volatile components of 0.01% orsmaller.

Polyvinyl alcohol expressed by the following formula (7) was dissolvedinto a mixed solvent of methanol and acetone (the ratio of amounts byvolume: 50:50), and a 5% solution was prepared. The obtained solutionwas applied to film (a4) obtained above using a bar coater to form alayer having a thickness of 1 μm, and the resultant layer was driedunder a stream of the warm air at 60° C. for 2 minutes. The surface ofthe resultant layer was subjected to the rubbing treatment, and a filmfor perpendicular orientation was prepared.

Modified Polyvinyl Alcohol

The film for perpendicular orientation prepared above was coated with acoating fluid containing 33.5% by weight of a discotic liquid crystalrepresented by formula (1) (i) shown above, 0.7% by weight of celluloseacetate butyrate, 3.1% by weight of a modified trimethylolpropanetriacrylate, 0.4% by weight of a sensitizer, 1.1% of aphotopolymerization initiator and 61.2% by weight of methyl ethyl ketoneto form a layer having a thickness of 3.5 μm, and the discotic liquidcrystal molecules were arranged in the homogeneous orientation. Then,the coating layer was irradiated with ultraviolet light from a mercurypump at an illuminance of 500 W/cm² for 1 second to polymerize thediscotic liquid crystal molecules. A film of optically anisotropicmember (A4) was obtained as described above. The discotic liquid crystalmolecules were arranged in the homogeneous orientation in a manner suchthat the slow axis was in the longitudinal direction of film (a4).

Optically anisotropic member (A4) had refractive indices of n_(xA):1.68296, n_(yA):1.58010 and n_(zA):1.68296, an in-plane retardationR_(e) of 360 nm, and a retardation in the direction of the thicknessR_(th) of −180 nm.

Preparation Example 8 Preparation of a Film of Optically AnisotropicMember (B4)

Unstretched single layer film (b4) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1600; the glass transitiontemperature: 163° C.] was obtained in accordance with the extrusionmolding. Unstretched single layer film (b4) was uniaxially stretched inthe longitudinal direction by a nip roll at a temperature of 136° C. ata stretching speed of 150%/min to a stretching ratio of 1.6, and a longsheet of a film having the slow axis in the longitudinal direction ofthe film, optically anisotropic member (B4), was obtained.

Optically anisotropic member (B4) had refractive indices of n_(xB):1.53117, n_(yB):1.53010, n_(zB):1.53010, an in-plane retardation R_(e)of 110 nm, a retardation in the direction of the thickness R_(th) of 55nm, and a content of residual volatile components of 0.01% or smaller.

Example 4 Preparation of a Liquid Crystal Display Device LCD-4

Optical element (a′4) was obtained by laminating the long sheet ofoptically anisotropic member (A4) obtained in Preparation Example 7 andthe long sheet of optically anisotropic member (B4) obtained inPreparation Example 8 in accordance with the roll-to-roll process in amanner such that the side of the layer of the discotic liquid crystal inoptically anisotropic member (A4) was placed towards opticallyanisotropic member (B4). The angle between the slow axis of opticallyanisotropic member (A4) and the slow axis of optically anisotropicmember (B4) was 0°.

Optical element (a′4′) was obtained by laminating a small film having alength of 40 cm and a width of 30 cm which was cut out of opticallyanisotropic member (a′4) (in a manner such that the transverse directionof optically anisotropic member (A4) was in the longitudinal directionof the small film) and the long sheet of polarizer plate (C) laminatedwith the low refractive index and the hard coat layer which was obtainedin Preparation Example IV in a manner such that the longitudinaldirection of the small film was parallel to the longitudinal directionof the long sheet and optically anisotropic member (B4) and polarizerplate (C) contact each other. The angle between the slow axis ofoptically anisotropic member (A4) and the absorption axis of thepolarizer plate was 90°. A plate obtained by cutting out of opticalelement (a′4′) obtained above was used as polarizer plate at the outputside (A′4).

A polarizer plate at the output side in a commercial liquid crystaldisplay device of the in-plane switching (IPS) mode was replaced withpolarizer plate of the output side (A′4). The members of the liquidcrystal display device were arranged in a manner such that theabsorption axis of polarizer plate of the output side and the in-planeslow axis of the liquid crystal cell under application of no voltagewere parallel to each other, and the absorption axis of polarizer plateof the incident side (A′4) and the in-plane slow axis of the liquidcrystal cell under application of no voltage were perpendicular to eachother, and a liquid crystal display device having the structure shown inFIG. 5, LCD-4, was prepared. The obtained device had a structure inwhich the members were disposed in the following order from the side ofvision of the liquid crystal display device: the low refractive indexlayer, the hard coat layer, the polarizer plate, the film of opticallyanisotropic member (B4) obtained in Preparation Example 8, the film ofoptically anisotropic member A4) obtained in Preparation Example 7, theliquid crystal cell and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-4 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Preparation Example 9 Preparation of a Film of Optically AnisotropicMember (A5)

A long sheet of unstretched film (a5) comprising a norbornene-basedpolymer [manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420R; the glasstransition temperature: 136° C.] and having a thickness of 100 μm wasobtained in accordance with the extrusion molding. Unstretched film (a5)obtained above had a content of residual volatile components of 0.01% orsmaller.

Polyvinyl alcohol expressed by the following formula (7) was dissolvedinto a mixed solvent of methanol and acetone (the ratio of amounts byvolume: 50:50), and a 5% solution was prepared. The obtained solutionwas applied to film (a5) obtained above using a bar coater to form alayer having a thickness of 1 μm, and the resultant layer was driedunder a stream of the warm air at 60° C. for 2 minutes. The surface ofthe resultant layer was subjected to the rubbing treatment, and a filmfor perpendicular orientation was prepared.

The film for perpendicular orientation prepared above was coated with acoating fluid containing 33.5% by weight of a discotic liquid crystalrepresented by formula (1) (ii) shown above, 0.7% by weight of celluloseacetate butyrate, 3.1% by weight of a modified trimethylolpropanetriacrylate, 0.4% by weight of a sensitizer, 1.1% by weight of aphotopolymerization initiator and 61.2% by weight of methyl ethyl ketoneto form a layer having a thickness of 4.1 μm, and the discotic liquidcrystal molecules were arranged in the homogeneous orientation. Then,the coating layer was irradiated with ultraviolet light from a mercurypump at an illuminance of 500 W/cm² for 1 second to polymerize thediscotic liquid crystal molecules. A film of optically anisotropicmember (A5) was obtained as described above. The discotic liquid crystalmolecules were arranged in the homogeneous orientation in a manner suchthat the slow axis was oriented in the longitudinal direction of film(a5).

Optically anisotropic member (A5) had refractive indices of n_(xA):1.68798, n_(yA):1.58066 and n_(zA):1.68798, an in-plane retardationR_(e) of 440 nm, and a retardation in the direction of the thicknessR_(th) of −220 nm.

Preparation Example 10 Preparation of a Film of Optically AnisotropicMember (B5)

Unstretched single layer film (b5) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420R; the glasstransition temperature: 136° C.] was obtained in accordance with theextrusion molding. Unstretched single layer film (b5) was uniaxiallystretched in the longitudinal direction by a nip roll at a temperatureof 138° C. at a stretching speed of 165%/min to a stretching ratio of1.7, and a long sheet of a film having the slow axis in the longitudinaldirection of the film, optically anisotropic member (B5), was obtained.

Optically anisotropic member (B5) had refractive indices of n_(xB):1.53219, n_(yB):1.53013, n_(zB):1.53013, an in-plane retardation R_(e)of 190 nm, a retardation in the direction of the thickness R_(th) of 95nm, and a content of residual volatile components of 0.01% or smaller.

Example 5 Preparation of a Liquid Crystal Display Device LCD-5

Optical element (a′5) was obtained by laminating the long sheet ofoptically anisotropic member (A5) obtained in Preparation Example 9 andthe long sheet of polarizer plate (C) laminated with the low refractiveindex and the hard coat layer which was obtained in Preparation ExampleIV in accordance with the roll-to-roll process in a manner such that theside of the layer of the discotic liquid crystal in opticallyanisotropic member (A5) was placed towards the polarizing plate. Theangle between the slow axis of optically anisotropic member (A5) and theabsorption axis of the polarizer plate was 0°.

Optical element (b′5) was obtained by laminating the long sheet ofoptically anisotropic member (B5) obtained in Preparation Example 10 andoptical element (a′5) obtained above in accordance with the roll-to-rollprocess. The angle between the slow axis of optically anisotropic member(B5) and the absorption axis of optical element (a′5) was 0°. A plateobtained by cutting out of optical element (b′5) obtained above was usedas polarizer plate at the output side (B′5).

A polarizer plate at the output side in a commercial liquid crystaldisplay device of the in-plane switching (IPS) mode was replaced withpolarizer plate of the output side (B′5). The members of the liquidcrystal display device were arranged in a manner such that theabsorption axis of polarizer plate of the output side (B′5) and thein-plane slow axis of the liquid crystal cell under application of novoltage were parallel to each other, and the absorption axis ofpolarizer plate of the incident side and the in-plane slow axis of theliquid crystal cell under application of no voltage were perpendicularto each other, and a liquid crystal display device having the structureshown in FIG. 6, LCD-5, was prepared. The obtained device had astructure in which the members were disposed in the following order fromthe side of vision of the liquid crystal display device: the lowrefractive index layer, the hard coat layer, the polarizer plate, thefilm of optically anisotropic member (A5) obtained in PreparationExample 9, the film of optically anisotropic member B5) obtained inPreparation Example 10, the liquid crystal cell and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-5 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Preparation Example 11 Preparation of a Film of Optically AnisotropicMember (A6)

A long sheet of unstretched film (a6) comprising a norbornene-basedpolymer [manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420R; the glasstransition temperature: 136° C.] and having a thickness of 100 μm wasobtained in accordance with the extrusion molding. Unstretched film (a6)obtained above had a content of residual volatile components of 0.01% orsmaller.

A resin expressed by the formula (5) shown above was synthesized inaccordance with the process disclosed in Makromol. Chem., Rapid Commun.10, 477-483 (1989). The synthesized resin in an amount of 8 g wasdissolved into 100 g of a solvent containing methanol and methylenechloride in relative amounts by weight of 2:8, and a solution of anazobenzene resin was prepared. Film (a6) obtained above was coated withthe prepared solution using a bar coater to form a layer having athickness of 4.0 μm. While the substrate was heated at 40° C., film (a6)was irradiated with linearly polarized light (light polarized in thedirection parallel to the transverse direction of the film (a6)) havinga illuminance of 11,000 lux obtained from a halogen lamp in thedirection perpendicular to film (a6) using an iodine-based polarizerplate, and a long sheet of a film having the slow axis in thelongitudinal direction of the film, optically anisotropic member (A6),was obtained.

Optically anisotropic member (A6) obtained above had refractive indicesof n_(xA):1.62866, n_(yA):1.52580 and n_(zA):1.62866, an in-planeretardation R_(e) of 360 nm, and a retardation in the direction of thethickness R_(th) of −180 nm.

Preparation Example 12 Preparation of a Film of Optically AnisotropicMember (B6)

Unstretched single layer film (b6) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420; the glass transitiontemperature: 136° C.] was obtained in accordance with the extrusionmolding. Unstretched single layer film (b6) was uniaxially stretched inthe longitudinal direction by a nip roll at a temperature of 133° C. ata stretching speed of 92%/min to a stretching ratio of 1.3, and a longsheet of a film having the slow axis in the longitudinal direction ofthe film, optically anisotropic member (B6), was obtained.

Optically anisotropic member (B6) had refractive indices of n_(xB):1.53091, n_(yB):1.53018, n_(zB):1.53018, an in-plane retardation R_(e)of 90 nm, a retardation in the direction of the thickness R_(th) of 45nm, and a content of residual volatile components of 0.01% or smaller.

Example 6 Preparation of a Liquid Crystal Display Device LCD-6

Optical element (b′6) was obtained by laminating a small film having alength of 40 cm and a width of 30 cm which was cut out of opticallyanisotropic member (B6) obtained in Preparation Example 12 (in a mannersuch that the transverse direction of optically anisotropic layer (B6)was in the longitudinal direction of the small film) and the long sheetof polarizer plate (C) laminated with the low refractive index and thehard coat layer which was obtained in Preparation Example IV inaccordance with the roll-to-roll process in a manner such that thelongitudinal direction of the small film and the longitudinal directionof the long sheet of polarizer plate (C) were parallel to each other.The angle between the slow axis of optically anisotropic member (B6) andthe absorption axis of the polarizer plate was 90°. A plate obtained bycutting out of optical element (b′6) obtained above was used aspolarizer plate at the output side (B′6).

Optical element (a′6) was obtained by laminating the long sheet ofoptically anisotropic member (A6) obtained in Preparation Example 11 anda long sheet of a polarizer plate [manufactured by SANRITZ Company;HLC2-5618] in accordance with the roll-to roll process in a manner suchthat the side of unstretched film (a6) of optically anisotropic member(A6) was placed at the side of the polarizer plate. The angle betweenthe slow axis of optically anisotropic member (A6) and the absorptionaxis of the polarizer plate was 0°. A plate obtained by cutting out ofoptical element (a′6) obtained above was used as polarizer plate at theincident side (A′6).

Polarizer plates at the output side and at the incident side in acommercial liquid crystal display device of the in-plane switching (IPS)mode were replaced with polarizer plate of the output side (B′6) andpolarizer plate of incident side (A′6), respectively. The members of theliquid crystal display device were arranged in a manner such that theabsorption axis of polarizer plate of the output side (B′6) and thein-plane slow axis of the liquid crystal cell under application of novoltage were parallel to each other, and the absorption axis ofpolarizer plate of the incident side (A′6) and the in-plane slow axis ofthe liquid crystal cell under application of no voltage wereperpendicular to each other, and a liquid crystal display device havingthe structure shown in FIG. 7, LCD-6, was prepared. The obtained devicehad a structure in which the members were disposed in the followingorder from the side of vision of the liquid crystal display device: thelow refractive index layer, the hard coat layer, the polarizer plate,the film of optically anisotropic member (B6) obtained in PreparationExample 12, the liquid crystal cell, the film of optically anisotropicmember (A6) obtained in Preparation Example 11 and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-6 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Preparation Example 13 Preparation of a Film of Optically AnisotropicMember (A7)

A long sheet of unstretched film (a7) comprising a norbornene-basedpolymer [manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1600; the glasstransition temperature: 163° C.] and having a thickness of 100 μm wasobtained in accordance with the extrusion molding. Unstretched film (a7)obtained above had a content of residual volatile components of 0.01% orsmaller.

A resin expressed by the formula (5) shown above was synthesized inaccordance with the process disclosed in Makromol. Chem., Rapid Commun.10, 477-483 (1989). The synthesized resin in an amount of 8 g wasdissolved into 100 g of a solvent containing methanol and methylenechloride in relative amounts by weight of 2:8, and a solution of anazobenzene resin was prepared. Film (a7) obtained above was coated withthe prepared solution using a bar coater to form a layer having athickness of 1.1 μm. While the substrate was heated at 40° C., film (a6)was irradiated with linearly polarized light (light polarized in thedirection parallel to the transverse direction of the film (a7)) havinga illuminance of 9,800 lux obtained from a halogen lamp in the directionperpendicular to the film (a7) using an iodine-based polarizer plate,and a long sheet of a film having the slow axis in the longitudinaldirection of the film, optically anisotropic member (A7), was obtained.

Optically anisotropic member (A7) obtained above had refractive indicesof n_(xA):1.62660, n_(yA):1.52660 and n_(zA):1.62660, an in-planeretardation R_(e) of 60 nm, and a retardation in the direction of thethickness R_(th) of −30 nm.

Preparation Example 14 Preparation of a Film of Optically AnisotropicMember (B7)

Unstretched single layer film (b7) comprising a norbornene-based polymer[manufacture by NIPPON ZEON Co., Ltd.; ZEONOR 1420R; the glasstransition temperature: 136° C.] was obtained in accordance with theextrusion molding. Unstretched single layer film (b7) was uniaxiallystretched in the longitudinal direction by a nip roll at a temperatureof 140° C. at a stretching speed of 190%/min to a stretching ratio of1.9, and a long sheet of a film having the slow axis in the longitudinaldirection of the film, optically anisotropic member (B7), was obtained.

Optically anisotropic member (B6) had refractive indices of n_(xB):1.53414, n_(yB):1.53000, n_(zB):1.53000, an in-plane retardation R_(e)of 360 nm, a retardation in the direction of the thickness R_(th) of 180nm, and a content of residual volatile components of 0.01% or smaller.

Example 7 Preparation of a Liquid Crystal Display Device LCD-7

Optical element (a′7) was obtained by laminating a long sheet ofoptically anisotropic member (A7) obtained in Preparation Example 13 andthe long sheet of polarizer plate (C) laminated with the low refractiveindex and the hard coat layer which was obtained in Preparation ExampleIV in accordance with the roll-to-roll process in a manner such that theside of optically unstretched film (a7) of optically anisotropic member(A7) was placed towards polarizer plate (C). The angle between the slowaxis of optically anisotropic member (A7) and the absorption axis of thepolarizer plate was 0°. A plate obtained by cutting out of opticalelement (a′7) obtained above was used as polarizer plate at the outputside (A′7).

Optical element (b′7) was obtained by laminating a small film having alength of 40 cm and a width of 30 cm obtained by cutting out of the longsheet of optically anisotropic member (B7) obtained in PreparationExample 14 in a manner such that the transverse direction of opticallyanisotropic member (B7) was in the longitudinal direction of the smallfilm) and a long sheet of a polarizer plate [manufactured by SANRITZCompany; HLC2-5618] in accordance with the roll-to roll process in amanner such that the longitudinal direction of the small film and thelongitudinal direction of the long sheet of a polarizer plate wereparallel to each other. The angle between the slow axis of opticallyanisotropic member (B7) and the absorption axis of the polarizer platewas 90°. A plate obtained by cutting out of optical element (b′7)obtained above was used as polarizer plate at the incident side (B′7).

Polarizer plates at the output side and at the incident side in acommercial liquid crystal display device of the in-plane switching (IPS)mode were replaced with polarizer plate of the output side (A′7) andpolarizer plate of incident side (B′7), respectively. The members of theliquid crystal display device were arranged in a manner such that theabsorption axis of polarizer plate of the output side (A′7) and thein-plane slow axis of the liquid crystal cell under application of novoltage were parallel to each other, and the absorption axis ofpolarizer plate of the incident side (B′7) and the in-plane slow axis ofthe liquid crystal cell under application of no voltage wereperpendicular to each other, and a liquid crystal display device havingthe structure shown in FIG. 8, LCD-7, was prepared. The obtained devicehad a structure in which the members were disposed in the followingorder from the side of vision of the liquid crystal display device: thelow refractive index layer, the hard coat layer, the polarizer plate,the film of optically anisotropic member (A7) obtained in PreparationExample 13, the liquid crystal cell, the film of optically anisotropicmember (B7) obtained in Preparation Example 14 and the polarizer plate.

When the property of display of the obtained liquid crystal displaydevice LCD-7 was evaluated by visual observation, it was found that theimages of display were excellent and uniform in the observationsdirectly in front of the display and in any oblique directions at anglesof 80° and smaller as the polar angle. Nonuniformity of the luminancewas not found in the observations directly in front of the display or inany upward, downward, rightward or leftward oblique direction at anyangle of 40° or smaller. No reflection of light from the outside wasfound. The reflectance at the wavelength of 550 nm was 0.53%, and themaximum value of the reflectance at wavelengths in the range of 430 to700 nm was 1.0%. No scratches were found in the test of scratchresistance.

Comparative Example 1

Polarizer plates in a commercial liquid crystal display device of thein-plane switching (IPS) mode were replaced with other polarizer plates[manufactured by SANRITZ Company; HLC2-5618]. The members of the liquidcrystal display device were arranged in a manner such that theabsorption axis of the polarizer plate of the output side and thein-plane slow axis of the liquid crystal cell under application of novoltage were parallel to each other, and the absorption axis of thepolarizer plate of the incident side and the in-plane slow axis of theliquid crystal cell under application of no voltage were perpendicularto each other, and a liquid crystal display device, LCD-8, was prepared.The obtained device had a structure in which the members were disposedin the following order from the side of vision of the liquid crystaldisplay device: the polarizer plate, the liquid crystal cell and thepolarizer plate.

When the property of display of the obtained liquid crystal displaydevice was evaluated by visual observation, it was found that images ofdisplay were poor due to insufficient contrast when they were observedin an oblique angle of 45° although the images of display were excellentwhen they were observed directly in front of the display. Reflection oflight from the outside was found. The reflectance at the wavelength of550 nm was 3.51%, and the maximum value of the reflectance atwavelengths in the range of 430 to 700 nm was 3.55%. Scratches wereclearly found in the test of scratch resistance.

INDUSTRIAL APPLICABILITY

The liquid crystal display device of the present invention exhibitsexcellent antireflection property and scratch resistance, prevents thedecrease in contrast in observation of the display at oblique angleswithout decrease in the quality of the images in observation directly infront of the display, provides a wide angle of field and achievesuniform display of images with great contrast at any angle ofobservation. The liquid crystal display device of the present inventioncan be advantageously applied, in particular, to the liquid crystaldisplay devices of the in-plane switching mode.

1. A liquid crystal display device of an in-plane switching mode whichcomprises a pair of polarizers which are a polarizer at an output sideand a polarizer at an incident side and disposed at relative positionssuch that absorption axes of the polarizers are approximatelyperpendicular to each other and at least optically anisotropic member(A), optically anisotropic member (B) and a liquid crystal cell whichare disposed between the pair of polarizers, wherein n_(zA)>n_(yA) andn_(xB)>n_(zB) when, with respect to optically anisotropic member (A) andoptically anisotropic member (B), refractive indices in a direction ofan in-plane slow axis are represented by n_(xA) and n_(xB),respectively, refractive indices in a direction in-plane andperpendicular to the direction of an in-plane slow axis are representedby n_(yA) and n_(yB), respectively, and refractive indices in adirection of a thickness are represented by n_(zA) and n_(zB),respectively, each measured using light having a wavelength of 550 nm,wherein the liquid crystal display device is in the followingconfiguration, wherein optically anisotropic member (A) and opticallyanisotropic member (B) are disposed between the polarizer at the outputside and the liquid crystal cell, the absorption axis of the polarizerat the incident side and the in-plane slow axis of the liquid crystal ofthe liquid crystal cell under application of no voltage are disposed atrelative positions parallel to each other, the in-plane slow axis ofoptically anisotropic member (A) and the in-plane slow axis of opticallyanisotropic member (B) are disposed at relative positions approximatelyparallel to each other, and the in-plane slow axis of opticallyanisotropic member (B) and the in-plane slow axis of the liquid crystalof the liquid crystal cell under application of no voltage are disposedat relative positions approximately parallel to each other, and whereinan in-plane retardation R_(e)(A), a retardation in the direction of thethickness R_(th) (A) of optically anisotropic member (A), and anin-plane retardation R_(e)(B), a retardation in the direction of thethickness R_(th)(B) of optically anisotropic member (B) satisfy thefollowing formulae:70≦R _(e)(A)≦120,−65≦R _(th)(A)≦−25,50≦R _(e)(B)≦110 and25≦R _(th)(B)≦70, wherein R_(e)(A)=(n_(xA)−n_(yA))×d_(A),R_(e)(B)=(n_(xB)−n_(yB))×d_(B),R_(th)(A)=[(n_(xA)+n_(yA))/2−n_(zA)]×d_(A),R_(th)(B)=[(n_(xB)+n_(yB))/2−n_(zB)]×d_(B), d_(A) and d_(B) representingthicknesses of optically anisotropic member (A) and (B), respectively,and the units of retardations in the formulae described above areexpressed by nm.
 2. A liquid crystal display device of an in-planeswitching mode which comprises a pair of polarizers which are apolarizer at an output side and a polarizer at an incident side anddisposed at relative positions such that absorption axes of thepolarizers are approximately perpendicular to each other and at leastoptically anisotropic member (A), optically anisotropic member (B) and aliquid crystal cell which are disposed between the pair of polarizers,wherein n_(zA)>n_(yA) and n_(xB)>n_(zB) when, with respect to opticallyanisotropic member (A) and optically anisotropic member (B), refractiveindices in a direction of an in-plane slow axis are represented byn_(xA) and n_(xB), respectively, refractive indices in a directioninplane and perpendicular to the direction of an in-plane slow axis arerepresented by n_(yA) and n_(yB), respectively, and refractive indicesin a direction of a thickness are represented by n_(zA) and n_(zB),respectively, each measured using light having a wavelength of 550 nm,wherein the liquid crystal display device is in the followingconfiguration, wherein optically anisotropic member (A) and opticallyanisotropic member (B) are disposed between the polarizer at the outputside and the liquid crystal cell, the absorption axis of the polarizerat the output side and the in-plane slow axis of a liquid crystal of theliquid crystal cell under application of no voltage are disposed atrelative positions perpendicular to each other, and the in-plane slowaxis of optically anisotropic member (A) and the in-plane slow axis ofoptically anisotropic member (B) are disposed at relative positionsapproximately parallel to each other, the in-plane slow axis ofoptically anisotropic member (B) and the in-plane slow axis of theliquid crystal of the liquid crystal cell under application of novoltage are disposed at relative positions approximately perpendicularto each other, and wherein an in-plane retardation Re(A), a retardationin the direction of the thickness R_(th)(A) of optically anisotropicmember (A), and an in-plane retardation R_(e)(B), a retardation in thedirection of the thickness R_(th)(B) of optically anisotropic member (B)satisfy the following formulae:30≦R _(e)(A)≦150,−90≦R _(th)(A)≦−15,40≦R _(e)(B)≦150 and20≦R _(th)(B)≦75, wherein R_(e)(A)=(n_(xA)−n_(yA))×d_(A),R_(e)(B)=(n_(xB)−n_(yB))×d_(B),R_(th)(A)=[(n_(xA)+n_(yA))/2−n_(zA)]×d_(A),R_(th)(B)=[(n_(xB)+n_(yB))/2−n_(zB)]×d_(B), d_(A) and d_(B) representingthicknesses of optically anisotropic member (A) and (B), respectively,and the units of retardations in the formulae described above areexpressed by nm.
 3. The liquid crystal display device according to claim1, wherein an absolute value of a difference between n_(xA) and n_(zA)is 0.003 or smaller, and an absolute value of a difference betweenn_(yB) and n_(zB) is 0.003 or smaller.
 4. The liquid crystal displaydevice according to claim 1, wherein optically anisotropic member (A)comprises a layer selected from following layers (i) to (iii): (i) Alayer comprising a material having a negative value of intrinsicbirefringence, (ii) A layer comprising discotic liquid crystal moleculesor lyotropic liquid crystal molecules, (iii) A layer comprising aphoto-isomerizable substance.
 5. The liquid crystal display deviceaccording claim 1, wherein optically anisotropic member (A) is disposedat a position closer to the liquid crystal cell than opticallyanisotropic member (B).
 6. The liquid crystal display device accordingto claim 2, wherein optically anisotropic member (B) is disposed at aposition closer to the liquid crystal cell than optically anisotropicmember (A).